Three, single-day nutritional surveys at weekly intervals were conducted in the general medical wards of an urban municipal teaching hospital. The techniques of nutritional assessment included anthropometric measures (weight/height, triceps skin fold, arm-muscle circumference, serum albumin, and hematocrit). The prevalence of protein-calorie malnutrition was 44% or greater by these criteria (weight/height, 45%; triceps skin fold, 76%; arm-muscle circumference, 55%; serum albumin, 44%; and hematocrit, 48%). These results were reproducible without significant variation between surveys. In 34% of patients, a lymphopenia of 1,200 cells/cu mm or less was found, a level likely to be associated with diminished cell-mediated immunity. Compared with a similar survey among surgical patients, the medical patients were more depleted calorically (weight/height, triceps skin fold) but had better protein status (arm-muscle circumference, serum albumin). Significant protein-calorie malnutrition occurs commonly in municipal hospitals in both medical and surgical services.