This study analyzed the nutritional status of cancer patients in relation to type and site of origin of the tumor, stage of disease, and previous chemical or radiation therapy. The analysis was performed on 321 patients (280 with cancer and 41 controls). The nutritional parameters included per cent of weight loss, anthropometric indices (arm circumference, triceps skinfold, arm muscle circumference), creatinine-height index, serum protein, albumin, total iron binding capacity and cholinesterase, C3 and C4 components of complement, total peripheral lymphocytes, and skin tests. The statistical comparison between patients with different tumors and controls, between patients with different stages of the same tumor, and between patients treated with or without previous chemical or radiation therapy led to the following conclusions: 1) malnutrition is mainly related to the type and site of origin of the tumor and, in the early stages of disease, is more pronounced in patients with cancer of the esophagus and stomach; 2) except in patients with breast and cervix cancer, malnutrition gets more severe as the disease becomes advanced; 3) chemical or radiation therapy has a variable impact on the nutritional status, but in selected patients it causes a drop in body weight, arm circumference, arm muscle circumference, and peripheral lymphocytes; 4) body weight, cutaneous delayed hypersensitivity and serum albumin are the most commonly altered parameters.