Mark Renton
Renton is the narrator and protagonist of the film, which follows his struggles in overcoming a heroin addiction and the negative influence of his friends. He is a morally ambiguous character, whose actions the audience can neither approve nor totally reject. Because the story is told through his eyes, not only in the narration but also the imagery, the audience develops an understanding and appreciation of some of his views of society, and some of his actions in response to his environment. However, it is also clear that he is not solely a victim—though some of his friends certainly have a negative impact on him, he also has a harmful impact on many of his friends. The audience is intended to identify with Renton and some of his ethically questionable decisions, a point that is driven home when he asserts, seemingly addressing the audience, “I am going to be just like you” in one of his closing lines.
Francis James Begbie
Begbie is one of the only characters in the film that does not take heroin. However, he is a much more despicable character than his friends that use heroin because of his predisposition for violence, his temper, and his abusive demeanor. He is constantly criticizing and verbally abusing Renton for his heroin addiction, despite his own issues, and in this way is used as a foil to Renton. Renton describes Begbie’s love for violence as “his own form of sensory addiction,” drawing a parallel to Renton’s own heroin use. He spends his free time trying to get into fights, and carries a switchblade that he pulls on people too easily, including his friends. All of his friends hate him, but feel like they cannot do anything to change him or abandon him because he is an old friend.
Tommy Mackenzie
Tommy starts the film as the ‘straight’ member of the gang: he does not take heroin, he does not cheat, and he does not lie. He has a serious girlfriend (Lizzie), a job, and a fixation on personal fitness. He is one of the characters who criticizes Renton’s addiction, and wants him to get off of drugs. However, his girlfriend breaks up with him after he loses their homemade sex tape (which Renton stole), and he goes into a downward spiral. He asks Renton to help him try heroin, intrigued by Renton’s assertion that heroin is better than sex and looking for something to ease the pain of his break up. He ends up addicted to heroin, contracts HIV from a used needle, and dies. His character shows reveals more clearly than anyone else the negative impact that Renton has on others.
Simon "Sick Boy" Williamson
Over the course of the movie, Sick Boy is a heroin addict, con man, small-time drug dealer, and pimp. He is antagonistic in his selfishness and his negative influence on Renton, in a similar way to Begbie, but is occasionally redeemed by displays of emotion, sympathy for his friends, and by comparison with Begbie. He thinks he is the cleverest member of his friend group, destined for something greater, and above his friends in his ability to break his addiction when he pleases. He is the most similar to Renton of the group, and as such is Renton’s closest friend, though Renton admits that he hates the ways that Sick Boy reminds him of himself.
Danny "Spud" Murphy
Spud is the kindest, least violent, and most incompetent member of the gang. He is often shown to be the least intelligent and most impressionable character, often simply nodding in agreement to things that others say. When he, Renton, and Sick Boy are found shoplifting and chased by security guards, Sick Boy escapes without being caught, Renton gets out of jail time, and only Spud is sent to prison. He silently nods in agreement as the Judge calls him a “habitual thief, devoid of regret or remorse.” He has a girlfriend, Gail, for most of the film, but it is revealed that she is intentionally depriving him of sex for her own amusement. His kind-heartedness does pay off in the end, when Renton feels sorry for him and decides to leave Spud’s share of the drug deal in a lockbox for him.
Diane Coulston
Renton sees Diane in a club, is impressed by her confidence and attitude, and pursues her, having rediscovered a libido that he lost while addicted to heroin. They have sex, but Renton finds out the next day that she is 15 years old. After waking up in her family home and meeting her parents, he is shocked and upset that he slept with a minor. Diane, however, wants to see Renton again, and threatens to tell the police that he slept with her if he refuses to see her again. Her insistence on keeping up a relationship bothers Renton, who would rather forget about the whole thing, and she is one of the mistakes that haunts him during his withdrawal nightmare sequence. He avoids her for much of the rest of the film, but she finds him again to ask if he has been tested for HIV, invites herself into his flat, and then initiates sex with again. She convinces him to make a life change, and he moves to London. She writes to him to keep in touch, but they do not meet again in the film.
Gail
Gail is part of the larger circle of Renton's friends, and she is Spud's girlfriend. She is characterized as somewhat selfish and cruel; she refuses to have sex with Spud simply because she enjoys watching him suffer. She does not use heroin, as far as we know.
Allison
Allison is one of Renton's friends who does heroin with him. She is the only woman to appear at Swanney's apartment with the friends as they shoot up, and rarely appears outside of this context. She is the mother of baby Dawn, and brings the baby to Swanney's apartment when she goes to shoot up. The baby dies because of her addiction-fueled neglect, and she is never seen again; she may have been arrested for criminal neglect, though it is not addressed.
Lizzie
Lizzie is part of Renton's larger group of friends, and is Tommy's girlfriend. She breaks up with Tommy, however, after he loses their homemade sex tape (though she also cites his lack of attention to her needs in general). This break up causes Tommy's downfall, as he turns to drugs, becomes addicted, and contracts HIV.
Gav
Gav is a peripheral friend of Renton's. He does not do heroin, and only appears occasionally in scenes in which all of the friends appear. He is used early in the film to make fun of the type of people who tell Renton to quit drugs, and to mock consumerism. He appears later in the film to explain Tommy's death to Renton.
