The aim of this study was to assess antibody response in 62 splenectomized patients and in 55 healthy subjects vaccinated with split influenza vaccine ("Fluarix," SmithKline Beecham). Response to hemagglutinin and neuraminidase was assessed before vaccination and after 1 month by hemagglutination inhibition test and neuraminidase inhibition test. After vaccination, antibody titers significantly increased in both groups. Postvaccination protection rates ranged from 62.9 to 90.3% in the splenectomized patients and from 81.8 to 94.5% in the control group. Response rates ranged from 50.0 to 75.8% and from 60.0 to 70.9%, respectively. Splenectomized patients produced high antibody levels regardless of the time elapsed from the operation to the vaccination. All requirements of the Committee for Proprietary Medicinal Products regarding humoral response to influenza vaccination in healthy people were fulfilled in both groups. The response in the splenectomized patients was comparable to that in the control group.