Since November 1981, 90 cancer patients treated with cytotoxic chemotherapy (CMF, FAC, FAM) have been studied to evaluate whether the administration of Synchrodyn 1-17, 100 micrograms i.m. a day for 15 consecutive days, could reduce some side effects caused by the cytotoxic drugs. Nausea, vomiting and weakness which are the most frequent side effects generally found to be very upsetting to patients, were less pronounced in the treated patients than in patients treated with a placebo. The performance status was not modified by the treatment. Skin pigmentation was noted in the majority of cases and it appeared to be related to the sustained treatment with high dosages of the peptide. Some side effects were observed in the treated patients such as sodium retention and hypertension, hyperglycemia. Successively we have begun to study the circadian rhythm of the cortisol, which often changes during the advanced stages of the illness and which chemotherapy does not seem to alter.