Abstract:One hundred thirty patients treated with anticancer drug therapy were analyzed. Alkylating agent toxicity was predominantly hematopoietic, antimetabolites and natural products produced equal incidence of hematopoietic and gastrointestinal toxicity. A minor degree of drug toxicity was necessary for response, but progressive toxicity did not increase responders. Responses were accompanied by prolongation of survival. Up to four previous courses of drugs did not prevent subsequent achievement of responses, nor increase drug‐induced toxicity. The latter findings may be due to natural selection of patients with slow growing tumors for repeated trials. Chemotherapy need not be pushed to severe toxicity to obtain responses. There was no evidence that chemotherapy was detrimental to patient survival.