Renal transplant recipients receiving immunosuppressive therapy are prone to major pulmonary infections. Development of influenza virus infection may lead to renal allograft damage or rejection. These patients should therefore be protected against influenza viruses by vaccination. A satisfactory antibody response was found in 12 (60%) of 20 renal transplant recipients vaccinated. Among 15 control subjects, the antibody response was satisfactory in all participants (100%). Factors that might play a role in suppression of antibody response include use of immunosuppressive drugs and renal allograft function. Immunization is safe and does not appear to affect renal allograft function.