Upon admission to hospital, 30-50 % of patients either are or become malnourished. There is no generally accepted definition of malnutrition or guidelines on the best way to establish nutritional status. We consider it self-evident that the nursing staff have an important role in screening patients at risk of malnutrition on admission and thereafter at regular times. This is why we developed the nursing nutritional screening form (NNSF). The NNSF was tested by nurses, dietitians and clinicians, in pairs, to establish the extent of agreement in two phases on sixty-nine and forty patients. Later, the form was used in practice by nursing staff on five wards (334 patients). Based on the results of the NNSF, patients were referred to a dietitian. The dietitian established whether the patient was indeed at risk, or was actually malnourished, using a complete nutritional history. The degree of concurrence within pairs was reasonable to good. The same applied to the concurrence between nursing staff and dietitians, but concurrence between clinicians and nursing staff was less. In total, 334 patients were screened and sixty-nine of them were referred to the dietitian. It was established that 86 % of the referred patients were potentially at risk of malnutrition or were malnourished. Without the NNSF, 39 % (n 27) of the patients referred to the dietitian would not have been referred, or would have been referred much later. The NNSF makes it possible for nurses to detect malnourished patients or patients at risk of malnutrition at an early stage of their hospitalization.