High-dose chemotherapy with peripheral blood stem cell transplantation (PBSCT) has become an important method of treatment for hematological and solid tumors. We examined levels of interleukin(IL)-4, interferon (IFN)gamma, soluble (s) CD30, and sIL-2 receptor (R) before and after autologous PBSCT, and compared findings for PBSCT with those for bone marrow transplantation (BMT). We found significantly higher IL-4 levels 1 and 3 weeks after PBSCT than before PBSCT, while IFNgamma levels remained almost unchanged after PBSCT. IFNgamma levels were increased 3 weeks after BMT, although no increase in IL-4 level was observed. The serum sCD30 level was significantly higher 3 weeks after PBSCT, but not following BMT. For 34 samples on days 0 and 21 from 17 patients undergoing PBSCT, a strong correlation was observed between sCD30 and sIL-2R levels (r = 0.43, P < 0.01). However, no significant correlation between sCD30 and sIL-2R levels was found for BMT patients. These findings suggest that sCD30 is a useful marker for evaluating immunological activity following autologous PBSCT, and that the immunological conditions after autologous PBSCT may be associated with helper-T-cell-2-type immune responses.