The sexual assault service, operated by the Children's & Women's Health Centre of British Columbia in partnership with the Vancouver General Hospital Emergency Department, started offering HIV prophylaxis in November 1996 to patients presenting to the emergency department after a sexual assault. In the first 16 months of the program a total of 258 people were seen by the service, of whom 71 accepted the offer of HIV prophylaxis. Only 29 continued with the drug treatment after receiving the initial 5-day starter pack, and only 8 completed the full 4-week treatment regmen and returned for their final follow-up visit. Patients at highest risk for HIV infection (those who had penetration by an assailant known to be HIV positive or at high risk for HIV infection [men who have sex with men, injection drug users]) were more likely to accept prophylaxis and more likely to complete the treatment than those at lower risk. Compliance and follow-up were the main problems with implementing this service. Service providers found it difficult to give the information about HIV prophylaxis to traumatized patients. After this program evaluation, the service changed its policy to offer HIV prophylaxis only to people at high risk of HIV infection. This targeting of services is expected to make the service providers' jobs easier and to make the program more cost-effective while still protecting sexual assault victims against HIV infection.