Since most patients with Hodgkin's disease benefit from splenectomy, a study was designed to explore whether these beneficial effects could be attributed to the recovery of patients' immunologic reactivity. Using a series of ordinary skin test (PPD-tuberculine, Varidase and Candidin) determination of absolute T and B lymphocyte counts in peripheral blood and their mitogenic responsiveness, assessment of immunologic reactivity was performed in 28 Hodgkin's disease patients, prior to and 14 days after splenectomy. The results showed that overall immunologic reactivity of these patients was suppressed as judged by low absolute lymphocyte counts (1747.2 +/- 171.9), lower counts of T (592.0 +/- 92.1) and B cells (295.9 +/- 40.5) and their poor capacity to respond to phytohemagglutinin (PHA) (20342.6 +/- 3662.8 cpm), although the reactivity towards skin test antigens seemed to be well preserved. After splenectomy the reactivity improved, absolute lymphocyte counts raised to 2654.9 +/- 468.8 and were parallelled by an increase in T (936.7 +/- 138.0) and B cell counts (402.2 +/- 81.2). PHA reactivity recovered as well (26965.5 +/- 4035.6 cpm), however, its remained lower than in control cultures. Furthermore, the immunocompetence of patients' spleens was assessed. The possible influence of some suppressive mechanisms such as serum-blocking factor and prostaglandins is discussed.