A phase I clinical trial was performed to detect adverse reactions in far advanced cancer patients treated with a unique specific cancer immunotherapy. The vaccines consisted of autologous tumor cell membranes and manganese phosphate gel. From 133 patients admitted into the trial, 95 vaccine batches were made. No batch was toxic in animals. One batch was bacteriologically contaminated. Sufficient patients survived or complied to receive 32 complete and 23 partial courses for a total of 707 SC and ID injections. Minor swelling and occasional minimal pain occurred at injection sites. There were two possible vaccine-related systemic reactions but no evidence of tumor transplantation, tumor acceleration, sepsis or autoimmune disease. Subjective and objective improvement occurred in a number of patients. The vaccines are safe. Their efficacy must be determined. The value of ID vaccine skin testing and the unexpectedly little bacteriological contamination require further study.