Forty patients with chemotherapy-related diarrhea were randomized to receive (i) octreotide 0.5 mg three times per day s.c. or (ii) loperamide 4 mg three times per day p.o. until complete remission of diarrhea was achieved. In the octreotide group 80% of patients showed complete resolution of loose bowel movements within 4 days of therapy, while in the loperamide group this goal was obtained in only 30% of cases (p < 0.001). If after 4 days no benefit was seen, patients were considered to have failed antidiarrheal therapy. Failure was recorded in only one case (5%) treated with s.c. octreotide and in five patients (25%) who received loperamide. The mean duration of antidiarrheal therapy necessary to achieve remission was 3.4 days in the octreotide group and 6.1 days in the loperamide group (p < 0.001). Treatment with octreotide was very well tolerated with mild abdominal pain in 15% of cases and pain in the injection site in 15% of patients. Subcutaneous octreotide is highly effective in the management of chemotherapy-related diarrhea in cancer patients.