Although the domestic pig is rapidly becoming an animal of choice in certain areas of biomedical research requiring a large animal model, effective utilization of the species is often encumbered by a lack of reference values for common functional variables. To address this problem, normal data for over 100 physiologic or related variables were collected from conscious chronically instrumented animals that were maintained under near basal conditions. Included were measurements of body composition, fluid volumes, blood physical and biochemical characteristics, blood gas and acid-base status, plasma hormone levels, energy metabolism, renal function, hemodynamics and pulmonary function. Most porcine values were similar to those collected under comparable conditions from humans. Compared to adult man, however, pigs had higher values for extracellular space, plasma volume, arterial pH, plasma bicarbonate, cardiac output, arterial pressure, expired ventilation, heat production, and core temperature, and lower values for red cell volume, hemoglobin level, plasma osmotic and oncotic pressure, arterial O2 content, renal blood flow and glomerular filtration rate. Many of these deviations were due to immaturity. Nevertheless, we have found pigs to be an excellent large animal model for a variety of functional studies.