Abstract Total pancreatectomy and intrasplenic autotransplantation of islet tissue was carried out in dogs. The resected pancreas was prepared by the partial islet isolation technique of gland distention, mincing and collagenase digestion. The influence of variations in technique was studied. Using otherwise identical methods, five collagenase lots were compared. Three lots were effective, resulting in successful transplants in 23 of 26 dogs. Two ineffective lots produced no successes in six dogs (p < 0.001). When minced particle size was varied, particles which would pass freely through a 16 gauge needle resulted in no successes in six dogs. With a larger particle size that would pass freely only through a 15 gauge needle, 15 of 15 transplants were successful (p < 0.001). When tissue was minced by hand, 8 of 11 transplants were successful, compared with 15 of 15 when mechanical mincing was used. With variation in collagenase concentration, success occurred in four of six using 300 units of collagenase/ml of minced tissue, in four of six using 600 units and three of six using 1,200 units. It is concluded that minced particle size and collagenase lot are critical variables in this technique of islet transplantation. Mincing method and concentration of collagenase do not appear to be important variables.