The effects of OK432, a streptococcal preparation, administered either orally (PO-OK432) or intratumorally (IT-OK432) on the immuno-reactivities of regional lymph nodes were investigated in gastric cancer patients. Although native lymph node lymphocytes (LNL) from untreated patients did not show any cytotoxicities against K562 and Raji cells, enhanced activities were found in LNL from patients administered OK432. Augmenting effects on the cytotoxicities of LNL by in vitro additional OK432, interleukin 2 or gamma-interferon were remarkable in the patients given IT-OK432. Moreover, the cytotoxicities of peripheral blood lymphocytes were augmented in vitro more strongly in patients given IT-OK432 than in those given PO-OK432. Flow cytometric analysis of LNL revealed a decrease in CD4+ cells by PO-OK432 and an increase in CD8+ cells by IT-OK432. An increase in CD4+2H4+ cells and a decrease in CD4+2H4- cells were observed in the patients given OK432, though CD8+CD11+ cells decreased by PO-OK432 while CD8+CD11+ cells increased by IT-OK432. Thus, it is suggested that LNL reactive to OK432 immunotherapy may differ between PO- and IT-OK432, and that the immunoreactivities of local lymph nodes and systemical immuno-reactivities may be highly potentiated by IT-OK432 rather than PO-OK432.