In Brazil, approximately 130 new cases of hepatitis A per 100,000 inhabitants occur annually and 15% of the population has been in contact with hepatitis B virus. Portal hypertension causes hypersplenism and reduces T cell production, which may lead to less effective response to hepatitis vaccination. The objective of the study was to evaluate the response to hepatitis A and B vaccination in patients with portal hypertension secondary to chronic liver disease or portal vein thrombosis. Twenty-three patients (2 to 18 years) with portal hypertension seen at the Pediatric Hepatology Service of Hospital das Clínicas, Universidade Estadual de Campinas, between 1994 and 2006 were studied. Hepatitis A and B serology was tested in all patients. Patients who had not been vaccinated before their visits received the vaccines during the study period. Patients who had been vaccinated before but had negative anti-HB antibodies received a booster dose, and their serology was repeated Blood counts were performed in each patient to assess for immunosuppression. Eighteen patients received hepatitis A vaccine and all became positive for anti-HAV antibodies. All patients had received hepatitis B vaccine and 17 (73.9%) were anti-HBs positive at the time of the study The other 6 received a booster dose and became anti-HBs positive afterward. The anti-HBs-positive and -negative patients did not differ significantly in age, leukocytes, lymphocytes, or duration between the vaccination and positive serology. In this study, hepatitis A vaccines elicited a 100% response and hepatitis B vaccine conferred protection and induced an anamnestic response in pediatric patients with portal hypertension.38187-93