Fatigue and malaise" (FM) is a frequent, non-specific symptom of cancer patients caused by the disease, its treatment and psychological distress. Since comprehensive quality of life assessment is often not feasible in multicentre clinical trials, short, but clinically relevant, quality of life indicators have to be defined. In a representative subsample of 127 patients in a phase-III randomized small-cell lung cancer trial comparing two different regimens of combination chemotherapy, quality of life was assessed at the beonning of each of the six treatment cycles with a self-rating questionnaire including an early version of the EORTC questionnaire, a mood adjective check list (Bf-S) and a single linear-analogue serf-assessment scale (LASA) measuring general well-being. FM, measured with a five-item Likert subscale of the EORTC questionnaire, showed moderate to high intercorrelations with other EORTC subscales assessing disease symptoms, toxicity of treatment, role functioning, personal functioning, restriction of social activity, psychological distress, emotional (Bf-S) and general well-being (LASA). At baseline, FM was one of the most pronounced symptoms. Over the six cycles 43%-31% of the patients complained of moderate to severe fatigue. Over the first two cycles FM tended to decrease, slightly increasing during cycles 3 and 4 and decreasing again before cycle 6. In a multiple regression analysis over the six cycles, 53% of the variance of FM was explained by patient-rated symptoms of disease and toxicity (disease alone: 43%; toxicity alone: 35%). Initial performance status, previous weight loss, treatment arm, cycle number and age predicted the scores of FM over the six cycles. We conclude that, among other disease-and Presented as an invited lecture at the 4th International Sympositmx Supportive Care in Cancer,