Planning the reorganization of a large medical clinic has been greatly facilitated through the use of systems analysis and model simulation techniques. This study describes a monitoring system utilizing the separate techniques of time-motion and work sampling which provides the input data for the models thus allowing an accurate simulation of actual clinic operations. Time-motion data is obtained by utilizing permanently installed automatic printing time clocks that record various times on a work sheet accompanying the patient's chart. Physician activity is determined by work sampling, a technique characterized by random observation sampling. An observation describes the type of physician activity concerned at an instant of time. Activity categories are charting, with patient, consulting and miscellaneous. In a typical week, 471 patients spent an average of 149 minutes in the clinic which included 80 minutes waiting, 8 minutes in exam room prior to physician beginning, 31 minutes physician time and 31 minutes of processing prior to leaving the clinic. The 2,587 observations of the physician group (103 physicians) obtained by work sampling, determined that they spend 37.8 per cent of their time charting, 5.3 per cent consulting, 55.2 per cent with the patient and 1.7 per cent in miscellaneous activities. Reproducibility of the data over months of obsrvaion suggest that it interferes minimally with clinic activity and is a reliable source of data for model simulation and evaluating operational changes.