All general practitioners at three Swedish health centres continuously assessed their patients' degree of functional deficiency on a 1-5 scale over a period of 5 1/2 years. They also registered diagnoses and certain other medical measures. Around 85% were judged to be ill to some degree, but few were seriously ill. There were small differences in functional capacity between men and women of different ages: both benign, self-limiting complaints and severe illnesses could be associated with considerable problems, while many patients with severe diseases had little discomfort. There was also a considerable discrepancy between functional impairment and work capacity. Using a combination of functional assessment with routine registration of diagnoses seems to be a useful method of obtaining a modulated, distinct picture of the types of patient encountering the general practitioner. However, further development work within the field is needed.