Forty-seven patients with renal carcinoma were included in first line or rescue protocols of immunotherapy including IL2 alone or in association with LAK cells, INF alpha or TNF. The toxicity was mild and the mortality was 2% (1 patient). The response rate was 26%. Nineteen children with neuroblastoma received IL2 either alone or in combination with LAK cells. The morbidity and mortality were higher in patients with end stage disease who had previously received high dose and prolonged chemotherapy. In contrast, the toxicity was mild and transient in patients treated in the months following autologous bone marrow transplantation. The only complete response observed was in 1 child treated with IL2, 4 months after high dose chemotherapy and ABMT. Immunological analysis showed that the immunomodulatory effect of IL2 is very different depending on whether IL2 is used alone or in combination with other cytokines; moreover, the biological effect of IL2 is dependent on the immunological status of the patients prior to IL2 therapy.