This paper describes a comparative analysis of questionnaire-based measures of functional status and clinical ratings of disability made by general practitioners and health visitors. Both approaches to functional assessment were used in rating 92 elderly primary care patients in terms of their performance of 13 mobility and self-help activities. Simple dichotomous and more complex trichotomous measures of performance were used to summarize functional ability in both the questionnaire and the provider's evaluation. Agreement between questionnaire-based and rater assessments was greatest for less complex mobility and self-help functions in comparisons using both dichotomous and trichotomous scales.