BACKGROUND: The viral safety of blood depends on donor selection and screening of the blood for viruses. OBJECTIVE: To determine the frequency of human immunodeficiency viruses 1 and 2, hepatitis B virus and hepatitis C virus in a population of donors. DESIGN: Retrospective study including all blood donations at a hospital-based transfusion unit between January 1995 and August 1998. RESULTS: A significant declining trend in the frequency of the human immunodeficiency virus from 4.5% in 1995 to 3.0% in 1998 was noted. Hepatitis B virus (HBV) decreased from 4.2% in 1995 to 3.9% in 1998, while hepatitis C (HCV) increased from 1.5% in 1996 to 1.8% in 1998. The changes for both HBV and HCV were not statistically significant. CONCLUSION: The safety of blood and blood products with respect to HIV, HBV and HCV is very high. It is important to educate donors regarding transfusion transmitted infections. It is recommended that HCV screening be implemented as a standard test for all donations.