Health professionals (HP) are frequently exposed to accidents with materials contaminated with blood and/or body fluids, thus representing a population at risk for the acquisition of human immunodeficiency virus (HIV) and hepatitis B virus (HBV). PURPOSE--To determine the prevalence of HIV and HBV infection among HP admitted to the University Hospital, Faculty of Medicine, University of São Paulo (UH-FMUSP), and to identify the possible sources of contamination. METHODS--A total of 345 HP who sequentially passed the hiring examination at UH-FMUSP from March 1 to June 23 1993 were evaluated and compared to 2521 blood donors using serologic tests for the detection of AgHBs and total anti-HBc of HBV. The ELISA method was also used for HIV-1, with subsequent confirmation by Western blot. Questionnaires were distributed to the HP for the identification of possible sources of contamination. RESULTS--Positivity to HIV-1 was 0.48% for HP and 0.23% for blood donors, and positivity to HBV was 8.89% and 6.17%, respectively. CONCLUSION--There was no statistically significant difference in the results of the serologic tests for HIV and HBV detection between the two groups, even taking into consideration the different professions of those who work in the health area and their potential exposure to blood and secretion.