In vitro, the combination of interleukin-2 (11–2) with interferon-α (IFN-α) seems to act synergistically on the generation of lymphokine activated killer (LAK) cells. Due to this fact two clinical trials with the combination of 11–2 and IFN-α were initiated in malignant melanoma (MM) and renal cell cancer (RCC). Patients with disseminated MM were treated by a sequential application of 10 × 106 U/m2 rlFN-α2b s.c. on days 1–7 followed by continuous intravenous infusion of 3 × 106 U/m2 rIl-2 on days 8–13 and 15–20. After a pause of 4 weeks the cycle was repeated. In advanced or disseminated RCC, the patients were treated with a daily alternating scheme of 10 × 106 U/m2 rIFN-α and rIl-2 as 1 h infusion 1 ×/day for 14 days. The rIl-2 escalates intra- and interin-dividually beginning with a dose of 3 × 106 U/m2. The cycles were repeated after a pause of 3 and 4 weeks, respectively. The preliminary results show that the schedules are practicable and that the toxicity of the combination of rIl-2 and IFN-α does not accumulate. Within the MM group 3/11 evaluable patients achieved partial remission and 2/11 stable disease. In the RCC-group 2/5 evaluable patients achieved partial remission and 2/5 had s