A vaccine consisting of four allogeneic colon carcinoma cell lines (DLD-1, HCT116, WiDr, and T84) mixed with the adjuvant DETOX (Mycobacterium phlei cell wall and Salmonella minnesota lipid A) was administered to 25 patients with low-volume metastatic colorectal carcinoma. The first eight patients received vaccine only, given intradermally on three occasions at 3-week intervals. Subsequent patients also received subcutaneous interleukin-1 alpha (IL-1 alpha), 0.3-0.5 microgram/m2 per day for 8 days after each vaccination in an outpatient setting. Vaccine alone caused local erythema, induration, and pruritus. IL-1 caused fevers, chills, and rigors that started in 4 h and lasted 1-2 h. One patient developed a brief loss of consciousness with a rigor that resolved without sequelae. One episode of mild hypotension occurred. Fatigue occurred by day 8 of IL-1. A substantial increase in the number of patients with positive skin tests to DLD-1 and HCT116 occurred after vaccine treatment both without and with IL-1 alpha. An allogeneic cell vaccine plus subcutaneous IL-1 was administered safely to outpatients with some evidence of in vivo effect observed.