PROLONGED partial perfusion presents problems that are not encountered or are of minimal importance in short partial or total perfusion. In our investigations we have delineated some of these problems and arrived at workable solutions. Briefly, the technique that we use is a simple venoarterial shunt without oxygenator. Blood is returned from the superior vena cava to a graduated venous reservoir, and from there through a DeBakey roller pump and arterial bubble trap to the femoral artery (Fig. 1). The dogs are given a continuous infusion of glucose, water, and saline during the perfusion. Various physiologic functions and blood chemistries were measured during the perfusion. Two series of 5 dogs each were perfused 24 and 48 hours, respectively. There were 3 long-term survivors in each series. The average perfusion rate was 44 cc. per kilogram per minute for the 24-hour series and 41.1 cc. per kilogram per minute for the