One hundred four consecutive patients with newly diagnosed small cell lung cancer, metastatic breast cancer, and ovarian cancer in good physical functional condition (performance rating 0-1 on Eastern Cooperative Oncology Group scale) were divided into a weight-losing group (> or = 5% unintentional weight loss within 3 mo; n = 48) and a weight-stable group (n = 56). Dietary intakes in relation to fat-free mass were not different in the two groups. According to the Quality of Life index and the General Health Questionnaire, weight-losing patients had significantly lower quality of life than weight-stable patients. In patients with weight loss, daily intakes of energy and protein correlated significantly with scores on the General Health Questionnaire. This study has shown that many ambulatory cancer patients do not eat enough to maintain weight and that even a moderate weight loss is associated with psychological distress and lower quality of life.