OBJECTIVE Main aim: to study the application of mixed prophylaxis against Hepatitis B viral infection (HB) in children injured by discarded needles and/or syringes. Secondary aim: to find in the group under study the incidence of HIV infection caused by these accidents. METHODS Descriptive study. METHODS 12 de octubre University Hospital, Madrid. METHODS Children injured by discarded needles and/or syringes and referred to the Preventive Medicine Service between May 1988 and April 1995 (7 years). METHODS 1) Serological study for HB and HIV; 2) application to unprotected children of HB mixed prophylaxis (specific Immunoglobulin--IGHB--plus vaccination) and 3) Post-vaccination serological check-ups for HB and HIV at 6 and 12 months from the incident. RESULTS 249 children, whose average age was 5.8 +/- 3.37, were seen (158 boys, 63.5% and 91 girls, 36.5%). 189 (75.9% of the total) received a dose of IGHB and 171 (71.8%) completed the HB vaccinations. Post-vaccination serological check-ups covered 144 children (84.2%). 101 children (40.6%) completed the HIV check-ups. No HIV infection was detected. CONCLUSIONS 1) HB mixed prophylaxis in children without serological protection is adequate for dealing with these incidents. 2) The risk of HIV infection should not be discounted, but is probably very slight. 3) The procedure should be put into practice in PC, with some shortening of HIV follow-up periods, as a measure to improve compliance.