Body weight maintenance is required in a variety of behavioral and physiological studies. A PC-based animal weighing system is described which features automated data collection and allows for accurate control of body weight in test animals via manipulation of food intake. Major system components are a PC-XT compatible computer, LOTUS 1-2-3 and measure software, and a digital electronic balance. The system is controlled by LOTUS macros which present menus to the user. Menus provide for the basic operations of the system, including establishing new data files, collecting weight data, printing, and transferring files to a laboratory minicomputer. The optional weight maintenance algorithm calculates the amount of food necessary to maintain target body weights. Some important aspects of this algorithm, including maintanance feeding and gain parameters, can be manipulated to reduce weight oscillation in test animals, or to accommodate the maintenance of body weight of different animal species. The system facilitates acquisition and recording of weight data, minimizes the frequency of error, and reduces variability both within and across animals when body weight maintenance is required.