From Dec 1986 to Dec 1990, 113 consecutive patients radically resected for renal cell carcinoma, have been randomized after surgery to observation or to Active Specific Immunotherapy (A.S.I.). 43 patients stage I-II and 13 p. stage III, according to TNM entered the treatment arm consisting of 10 autologous irradiated tumor cells injected intradermally, either mixed with BCG 10(7) (on days 28th and 35th after surgery) or alone (on day 42th). At randomization and 1, 6 and 12 months after treatment, patients were evaluated for the development of a DTCH to autologous tumor and to autologous normal cells, obtained by mechanical and enzymatic dissociation of the surgical specimens. Baseline DTCH were negative in all patients. One month after completing A.S.I. 36 out of 50 evaluable patients displayed a significant DTCH response to autologous tumor, which remained positive in 23/40 patients at 6 months. Our data clearly indicate that Active Specific Immunotherapy with autologous tumor cells mixed with BCG can elicit a specific immune response to autochthonous tumor as measured by DTCH.