The incidence of nosocomial infections (NI) and the related risk factors in a Department of Pediatric Cardiovascular Surgery were studied, during a 6 months period. 155 successive admissions were considered. Nosocomial infections were 17 (11%), nosocomial colonizations 18 (11.6%). The most important risk factors for nosocomial infections were: age, cyanosis, duration of hospitalization, hospitalization in Intensive Care Unit and central venous catheter only as a risk factor for sepsis. The most important risk factors for nosocomial colonizations were: tracheal intubation and central venous catheter. In 4 cases the NI was related to nosocomial colonization (2 sepsis, 1 pneumonia, 1 wound infection). The most frequently isolated microorganisms were Pseudomonas aeruginosa and Staphylococcus spp. The Authors found that a longer than 5 days period of antibiotic prophylaxis did not reduce the incidence of nosocomial infections.