Vincent is an "invalid" or "de-gene-erate" who strives to become a space navigator for the flights to Titan. Vincent strives against the gene-ism that is prevalent and eventually has to take the identity of Jerome Morrow in order to achieve his goal. Vincent explains how he achives his goals in life when he explains to his brother that he wins by "never saving himself for the swim back".
Jerome MorrowJude Law
Jerome Morrow is a "valid", a genetically manipulated individual who is the norm for society. Upset with the world and the fact that even with all these genetic modifications he still comes second, Morrow attempts to commit suicide. Unsuccessful "even at this", Morrow attempts to fuel his lifestyle by deciding to aid an "invalid" in achieving their ambition. Vincent enters the scene, he takes the identity of Jerome (who reverts to his middle name of Eugene) and befriends Morrow. Whilst Vincent lives his life and schieves his own ambitions, Jerome must satisfy himself with being a wheelchair-ridden donor in order to maintain the deception. Morrow taunts Vincent about his genetic superiority, and often likes to intimidate others, often to the point of bravado-style boats and jibes. Eventually when Vincent has achieved his goal, Jerome finds that his life has been enriched "I may have given you my body, but you have given me your ambitions". Finally Jerome finds his peace at the end of the film.
IreneUma Thurman
Irene is the "Valid" who wasn't quite up to spec. Irene wanted to go into space, just like Vincent, but the unnacceptable heart condition percentage that was discovered put paid to that. Irene works in the Gattaca company and falls for Vincent when he starts to work there under the identity of Jerome. Irene has Vincent "sequenced" and, believing he is Jerome, asks him out for a date. Eventually Vincent's deception is discovered by Irene, and she has to decide whether to accept Vincent as the "Invalid" who is leading a life of deception, or to reject him for being the liar he is.
Anton Freeman
Younger brother of Vincent, Antin was given his father's name and considered to be the worthy successor. Often used his status as a "valid" to taunt Vincent, until he was finally beaten during their final game of "chicken" where they swim out as far as they dare until one of the brothers chickens out. Anton never aspires to much and only ever becomes a police officer.
DetectiveAlan Arkin
Caesar, the Head CaretakerErnest Borgnine
Cheerful old-timer who always has some friendly, humerous put-down for the junior cleaners: "You like space, eh? Here's a space that needs you to clean it". The Head Cleaner is most probably an "invalid", who has accepted his fate that he, and others like him, are fated to only aspire to be cleaners, and that only "valids" will actually ever work in the Gattaca company. A man who only knows his job, the Head Cleaner finds the murder investigation to be a confusing distraction from his job.