Biological response modifiers (BRMs) have greatly modified the immunotherapy of tumors. Interleukin-2 (IL-2) has brought about metastasis regression in some cases of malignant tumors, however, when given systemically, it results in high toxicity. More recently, the subcutaneous administration of IL-2 (combined with alpha-interferon, alpha-IFN) seems to be capable of offering the same chances of therapeutic response, but this time with a lower level of toxicity. The Authors report an evaluation of toxicity in 22 patients treated with a combination of IL-2 + alpha-IFN i.m. with or without chemotherapy. The side-effects present in the majority of cases were: fever, diarrhea and asthenia. Approximately 50% of the patients had nausea/vomiting, mucositis, skin rashes, and slight leukopenia. The following side-effects were noted to a much lesser degree, thrombocytopenia, alterations in hepatic and dizziness and cystitis. Only one patient reached 4th degree toxicity, with mucositis, asthenia and skin rash. All the other patients received the treatment without suspensions for toxicity. Biological evaluations will enable us to determine in the future, the cases which can benefit from therapeutic intensification and thus it would seem opportune at this time to use therapy with acceptable toxicity.