Physicians wishing to maintain the functional capacity of their patients often need, but usually do not have, practical measures of function. The Dartmouth COOP, a primary care research network, developed nine pictorial Charts to efficiently measure patient function in busy office practice. Each Chart has a five-point scale, is illustrated, and can be self-administered or administered by office staff. The Charts are used to measure the patients' overall functional health just as Snellen Charts are used to measure vision. Studies to assess the Charts' reliability, validity, acceptability and clinical utility were conducted on over 2,000 patients in four diverse clinical settings. Results show that the Charts are both reliable and valid. One-hour test-retest intraclass correlations for elderly patients ranged from 0.78 to 0.98 and from 0.73 to 0.98 for low income patients. The average Pearson product-moment correlation between Charts and previously validated measures of function was 0.61 and the Charts were as capable of detecting the association between disease and functioning as were longer, standard measures. Most clinicians and patients report that the Charts are easy to use and provide a valuable tool to measure overall function in busy office practice. For the 25% of patients in which the Charts uncovered new information, changes in clinical management were initiated for 40% of them. We conclude that the COOP Charts are practical, reliable, valid, sensitive to the effects of disease and useful for quickly measuring patient function.