Seventy-four patients with Dukes' B2 through C3 colon or rectal cancer were entered into a prospectively randomized, controlled trial of active specific immunotherapy (ASI) with an autologous tumor cell-BCG vaccine. Primary tumors were dissociated enzymatically and cryopreserved by techniques that maintain cell viability. Patients were randomized into groups treated by resection alone (control) or resection plus ASI. All patients with rectal cancer received 5,040 rads of pelvic irradiation post-operatively. With a median follow-up of 56 mo, there is a moderately significant difference in the distribution of time-to-recurrence (P = .037) and a comparably significant difference in the distributions of time-to-death (P = .031); both comparisons favor the ASI group. Most of the difference was due to the subgroup with colon cancer. With such small numbers of patients, we cannot conclude that ASI is of proven therapeutic benefit. The results are sufficiently encouraging that the trial is continuing and a national multi-institutional prospectively randomized trial is being conducted.