Thirty Egyptian males, 8–31 years of age, with active Schistosoma mansoni infection and negative serologic tests for hepatitis B markers, were vaccinated with a recombinant hepatitis B vaccine (Merck's Recombivax®). The vaccine was given intramuscularly in the deltoid region in three 10 µg doses at 0, 1, and 6 months. All patients were treated with praziquantel 2 months after the first vaccination. Sera were collected every 2 months for 12 months and tested for anti-HBs using a quantitative ELISA technique. There were no side reactions except for mild local soreness at the injection site in 3 patients. At 12 months, all subjects seroconverted (antibody levels > 10 mIU/mL); 24 patients (80%) developed antibody levels > 1,000 mIU/mL. As with a plasma-derived vaccine, antibody levels were negatively correlated with increasing spleen size. A recombinant hepatitis B vaccine was safe and immunogenic when given to patients with schistosomiasis mansoni.