Soluble interleukin-2 receptor (sIL-2R) levels were measured in sera from 33 patients with metastatic malignant melanoma and 14 patients with metastatic or advanced renal cell cancer. Significantly elevated levels were found in both groups compared to 30 healthy controls. No correlation was found between the levels of sIL-2R and clinical parameters such as disease-free interval and tumour burden. Neither was there any correlation between receptor-levels and survival. This contrasts with the observations in lymphoma patients, but is in accordance with findings in other solid tumours. sIL-2R is possibly a marker of the host immune response to the tumour, but further investigations are needed to see if it has any predictive value concerning prognosis or response to immune therapy.