Uremic patients are at high risk of hepatitis B virus (HBV) infection and, despite the availability and efficacy of hepatitis B vaccine, a high rate of non responders has been reported. Forty uremic patients undergoing maintenance hemodialysis who failed to produce any measurable anti-HBs antibody response after 4 administrations of 5 micrograms of Hevac B Pasteur vaccine were admitted to a randomized controlled clinical trial. Group A (14 patients) received 3 doses of 5 micrograms s.c. each of vaccine at monthly intervals and 12 doses of 50 mg s.c. of thymopentin on alternate days between the first and the second vaccination. Group B (11 patients) received 3 doses of 5 micrograms s.c. each of vaccine at monthly intervals. Group C (15 patients) received 3 doses of 10 micrograms s.c. each of vaccine at monthly intervals. Immunization rates were 86% in group A (on both 1-month and 6-month checks), 36% on the 1-month and 27% on the 6-month check in group B, 53% on the 1-month and 47% on the 6-month check in group C. Anti-HBs antibody titers were similar in group A and C but notably lower in group B. Thymopentin seems as useful therapeutical tool for non responder patients. As it promotes T cell maturation and responsiveness, which are impaired in uremia, it could play a major part in the management of uremic immunodeficiency.