Delayed hypersensitivity and lymphocyte subsets in a group of adult splenectomized patients after abdominal trauma without associated disease have been studied. The results were compared with those observed in healthy individuals. The results show a decreased cutaneous reaction against extracts of Streptococcus and diphtheria antigens. Moreover, an increase in the number of lymphocytes and monocytes was observed, but the T4/T8 ratio was not affected. The impaired cutaneous response against Streptococcus could be related to post-splenectomy sepsis.