We conducted a prospective quality-of-life analysis during outpatient immunotherapy in 22 patients with progressive metastatic renal cell carcinoma (RCC) treated with subcutaneous interferon-alpha2a and subcutaneous interleukin-2. Patients' quality of life was assessed by the European Organization for Research and Treatment of Cancer quality-of-life questionnaire QLQ-C30 before (week 0) and once during immunotherapy (week 3). Advanced renal cancer patients completed a total of 30 questionnaires before therapy (week 0) and after 3 weeks of therapy. Their mean quality of life (global-quality-of-health status) deteriorated significantly, from 64 to 41 (P</=0.001) during the first 3 weeks after treatment initiation, due to a mean reduction in physical (from 82 to 65; P</=0.001), emotional (from 77 to 61; P</=0.01), social (from 78 to 55; P</=0.01), and role functioning (from 82 to 58; P</=0.01). In contrast, cognitive functioning did not differ significantly from pretreatment scores after 3 weeks of therapy. In addition, during the first 3 weeks, appetite loss (from 18 to 59; P</=0.01), fatigue (from 33 to 56; P</=0.01), nausea/vomiting (from 10 to 26; P</=0.01), sleep disturbance (from 27 to 47; P</=0.01), diarrhoea (from five to 27; P</=0.01), and pain (from 20 to 32; P</=0.05) were significantly increased, while quality-of-life symptoms such as dyspnoea, and constipation were not significantly influenced by therapy. Complete response to RCC outpatient immunotherapy was associated with the most predominant reduction in functional quality of life when compared against patients in progressive or stable disease or partial tumour response. In conclusion, quality-of-life analysis during outpatient immunotherapy yielded modest changes in patients' health status 3 weeks after therapy initiation. Since the rapid decline in functional quality-of-life was associated with therapeutic efficacy, it is suggested that quality-of-life analysis might serve as an early indicator for immunotherapy response in metastatic RCC. British Journal of Cancer (2003) 89, 50-54. doi:10.1038/sj.bjc.6600996 www.bjcancer.com