To evaluate of adjuvant immunochemotherapy with PSK in curatively resected colorectal cancer, randomized controlled study by 35 institutions in Kanagawa prefecture was conducted. From March 1985 till February 1987, 462 patients were assigned one of two different regimens. 448 patients (97.0%) of them satisfied the eligibility criteria. Control group received mitomycin C intravenously on the day and the day after the operations respectively followed by 5-FU orally over for 6 months. PSK group received in addition to mitomycin C and 5-FU as in control group, PSK orally for over 3 years. By February 1989, follow up studies of the patients after their operations had been carried out for two years to four years. The disease free curve and the survival curve of PSK group were higher than those of control group, differences between the two groups were statistically significant (Disease free curve: P = 0.0096, survival curve: p = 0.0391). From these results, adjuvant immunochemotherapy with PSK was considered beneficial for curatively resected colorectal cancer.