MCNU is a new derivative of nitrosourea and experimental studies have shown equal or superior activity to known nitrosourea compounds. Twenty one cases were entered into our clinical studies with a phase II study. Nineteen cases have had a several courses of prior chemotherapy. Four out of 21 cases achieved a partial response (each one of lymphoepithelioma, parotid gland cancer, recurrent uterine cancer and recurrent breast cancer). The major toxicity encountered during treatment was myelosuppression. Full recovery of myelosuppression was delayed and was seen six to eight weeks after each injections. These initial results justify further clinical investigations with MCNU.