This paper reviews the development in defining and measuring the patient's functional status. It reflects the work of an international working party. Functional status is defined as: 'the ability of a person to perform and adapt to the individual's given environment, measured both objectively and subjectively over a stated period of time'. The Dartmouth COOP Functional Health Assessment charts/WONCA (COOP/WONCA charts) are the adaptation for international use in (general) practice of the Dartmouth COOP Functional Health Assessment Charts. They cover the domains of Physical Fitness, Feelings, Daily Activities, Social Activities, Change in Health and Overall Health, providing a generic, patient-oriented instrument. They have been extensively used in chronic diseases, where their acceptability to patients and clinical validity were satisfactory. Their limitations (particularly the quantification and exact interpretation of the scales) do warrant further study. Nevertheless, general practitioners and others are encouraged to use the COOP/WONCA charts.