Mark, often called "Rents," is an intelligent young man living in Leith who dropped out of university. He actively participates in the local heroin scene but retains a strong interest in literature and philosophy. He routinely masks his intellect to blend in with his peers and manipulates the welfare system to secure income without holding a job. He attempts to quit heroin on multiple occasions but continually returns to his addicted social circle.

Known as "Sick Boy," Simon is deeply entrenched in the local drug scene alongside his friends. He fashions himself as a suave womanizer and idolizes Sean Connery, actively emulating the actor's James Bond persona. He maintains a high degree of confidence and focuses his daily routine on securing his next high and finding his next sexual conquest.

Danny, nicknamed "Spud," is a gentle and empathetic member of the local friend group. He relies on government welfare to support his lifestyle, though he lacks the manipulative edge of his peers. He shows a surprising capacity for compassion, stepping up to defend innocent animals and family members against cruelty even when outnumbered.

Frank, or "Franco," is a violently unpredictable member of the group who avoids heroin but consumes heavy amounts of alcohol. He actively seeks out physical altercations in local pubs and expects total loyalty from his friends. He relies on intimidation and brute force to maintain control over his social circle and his romantic partner.

Tommy initially stands out from the rest of the group because he prefers speed and alcohol over heroin. He is physically fit, relatively handsome, and derives a sense of status from his relationship with his fiercely strong-willed girlfriend. A personal setback eventually pushes him toward the drug habits of his friends.

Davie experiences a highly turbulent personal life in Edinburgh. Following a devastating HIV diagnosis linked to a trauma experienced by his girlfriend, his focus shifts toward attending a self-help group. He harbors a deep, calculating anger and actively plots against the man he holds responsible for his illness.

Matty is a peripheral member of the Edinburgh drug scene who is deeply involved in the local punk culture. He faces the severe health risks associated with needle sharing in his community. He is also a father, a role that occasionally grounds his chaotic existence in the eyes of his peers.

Stevie is a childhood friend of the central group who moved away from the local drug scene. Having relocated to London, he finds himself increasingly disconnected from his old friends' chaotic lifestyles. He focuses his energy on building a stable life and nurturing his romance with his girlfriend.

Kelly is a resilient, university-enrolled young woman who works in a local pub. She acutely understands the pervasive misogyny in her environment and refuses to accept it passively. She frequently leans on female solidarity and executes private acts of revenge against abusive patrons to fight back against the men who disrespect her.

Billy is Mark's brother and a soldier in the British army. His military service deeply annoys Mark and creates political tension within the family. His life choices place him on a completely different path from his heroin-addicted brother.

Davie is Mark and Billy's brother. He lived with a severe disability and passed away before the main events of the story. His life and passing heavily impact the Renton family dynamic and deeply influence Mark's psychological struggles.

Nina is Mark's teenage cousin. She projects an aloof and moody exterior to cope with uncomfortable family gatherings. Unlike the others, she is untouched by the local heroin scene and retains a level of youthful innocence beneath her attempts to seem detached.

June is Frank's pregnant girlfriend. She lives in a dangerous situation, constantly subjected to Frank's unpredictable aggression and emotional abuse while attempting to maintain their relationship.

Johnny, known as "Mother Superior," is a prominent local drug dealer favored by Mark and Simon for his high-quality heroin. He hosts shooting-up sessions in his home and maintains a dark sense of humor regarding the extreme risks his lifestyle entails.

Alan is an ill, deeply unpleasant man attending a support group. He committed a horrific assault against Davie's girlfriend, setting off a tragic chain of infections. He remains a focal point of Davie's obsession.

Dianne is a teenager who looks older than her fourteen years. She connects with Mark over a shared interest in music, confidently bringing him home without revealing her true age or the fact that she lives with her parents.

Dawn is the infant daughter of Simon and Lesley. Her fragile presence briefly forces the group of addicts to confront the harsh realities of life, responsibility, and the consequences of their environment.

Mike is a drug dealer whom Mark visits when Johnny Swan is unavailable. He exerts power over desperate addicts, deliberately withholding drugs and insulting them for his own amusement before handing over alternative substances.

Giovanni is an older Italian immigrant living in self-imposed exile in London. Carrying the burden of a family scandal back in Italy, he seeks companionship in seedy environments.

Goagsie is a local figure frequently referenced by the group. He represents the ever-present specter of illness within the community, serving as a grim reminder of the fatal risks associated with their lifestyle.

Julie is a local woman whose tragic illness highlights the extreme stigma surrounding the local epidemic in the 1980s. Her fate leaves a lasting impression on the community.

Maria is a young woman struggling with heroin addiction who occasionally sleeps with Simon. She finds herself in vulnerable positions, subjected to exploitation by the men around her who seek to profit from her desperation.

Alison is deeply embedded in the local heroin culture, providing a sharp female perspective amidst the male-dominated group. She asserts her own desires aggressively and leans on moments of female solidarity to handle the frequent misogyny around her.

Lesley is a young mother entangled in the local drug scene. She experiences devastating personal trauma but struggles to separate herself from her addiction, immediately seeking out the numbing effects of heroin to cope with her reality.

Lizzy is Tommy's strong-willed girlfriend, described by him as a "pure steel woman." She commands respect and status, but her fiery temper and intolerance for Tommy's priorities eventually cause a rift between them.

Uncle Dode is Danny's uncle, a man of mixed ethnicity who faces severe and violent racism from local skinheads. He defends himself bravely but relies on the support of his family when violently targeted.

Na Na is Danny's grandmother. She is a matriarchal figure with a colorful romantic history, having had various children with different men throughout her life.

Second Prize is a local friend of the main group who struggles heavily with alcohol addiction. He frequently borrows money and is known for his drunken, destructive behavior.

Gav is part of the broader social circle in Leith. He offers Mark a place to stay during funerals and actively tries to manage the chaotic behavior of friends like Second Prize.

Mark's mother is a long-suffering matriarch who desperately tries to help her son kick his heroin habit. She endures repeated heartbreaks over the fates of her children but refuses to give up on attempting to cure Mark through home-based rehabilitation.

Mark's father takes a hardline approach to his son's addiction, enforcing strict cold-turkey rehabilitation at home. He has complex unionist political views and harbors a quiet resentment that frequently clashes with Mark's own worldview.

Mrs. Murphy is Danny's mother, who carries a deeply protective and somewhat naive view of her son. She blames Mark and Simon for dragging Danny into addiction, a belief that shatters when confronted with harsh truths.

Stella is Stevie's girlfriend in London. Her reciprocal declaration of love provides Stevie with the emotional anchor he needs to fully separate from the toxic Edinburgh drug scene.

Donna is Davie's girlfriend, who becomes the victim of a brutal assault by Alan Venters, leading to a tragic chain of health consequences that forever alters her and Davie's lives.

Lisa is Matty's young daughter. She stands as the sole beacon of hope and innocence in Matty's otherwise chaotic and prematurely shortened life.

Frank's father is an older, alcoholic man who haunts the abandoned Leith Central Station. His sarcastic remarks about "trainspotting" give insight into the bleak generational cycles of addiction and neglect that shaped his son's violent nature.

Sharon is Billy's widow. She harbors dark secrets about her abusive marriage to Billy, seeking brief and inappropriate solace with Mark during a moment of intense familial mourning.