Hospital infections play an important role in the increase of patients' morbimortality and hospitalization costs, especially in the case of individuals admitted to intensive care units (ICU) during postoperative heart surgery. Analysis of the epidemiological profile of the hospital infections in the pediatric-ICU (P-ICU) of Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, University of São Paulo (HCFMRP-USP) demonstrated a 31.1% incidence of pneumonia (PNM) and a rate of ventilator-associated pneumonia (VAP) of 23.81 per 1000 ventilators-day between March 2004 and February 2005 in the group submitted to cardiac surgery. Knowledge of the pathophysiology and risk factors associated with this infection allows for measures aiming at reducing its incidence. The objective of the present study is to evaluate the effect of oral hygiene with a 0.12% chlorhexidine solution on the incidence of PNM and PAV in children submitted to cardiac surgery.