Long-stay wards, where patients are permanently resident, have a responsibility to ensure that the diet that they provide is adequate to meet their residents' needs. The diets of long-stay, elderly patients with mental health problems were assessed and compared with dietary reference values. The nutritional Value of the food supplied from the kitchen and the ward, the food served to the patient and the food consumed by the patient was evaluated. Results showed that food wastage, as service losses and plate waste, had nutritional implications. In the cases of vitamin C, riboflavin, vitamin B-6, vitamin A, calcium, iron, copper, zinc and total energy, the amounts available to patients were adequate. After service losses and plate waste however, intakes were found to be low. In other cases the food available would not have supplied adequate amounts of the nutrients, even if no losses had occurred [folate, vitamin D, magnesium, potassium, iodine, selenium and dietary fibre). Actual intakes of some nutrients, notably heat labile vitamins, may be lower than recorded owing to the effects of catering practices (e.g. warm-holding). Low intakes usually resulted from a combination of service losses and plate waste. Plate waste occurred for a number of reasons, including inappropriate eating utensils, unfamiliar or disliked foods and insufficient time for meals.