The UW solution developed for cold storage of the liver, pancreas, and kidney was used in a modified form in this study and tested in the orthotopic transplantation of dog livers, kidneys, and pancreases preserved for 48 hr. The modification was the alteration of the concentrations of potassium and sodium. The original UW solution contained 120 mM K+and 30 mM Na+. In this study the Na+was 140 mM and the K+only 9 mM, all other agents were identical to the original UW solution. Six of 11 dogs survived with livers preserved for 48 hr. The five deaths were due to technical complications and unrelated to preservation failure. Postoperative AST and partial thromboplastin time (PTT) values were lower (statistically significant on days 1, 3, and 4) in livers preserved in the high Na+UW solution than as previously shown in the high-k+UW solution. Other measures of liver function (bilirubin and fibrinogen) were similar between the high-Na+and high-K+groups. Six dogs survived with kidneys preserved for 48 hr in the high-Na+UW solution. The results were comparable to those obtained with the high K+solution. Four of six dogs survived for up to 28 days with pancreases preserved for 48 hr. The two deaths were due to technical complications unrelated to preservation failure. Three of the four dogs had normal blood glucose values for one month, and intravenous glucose tolerances test on day 7 and 28 were identical to those obtained in pancreases preserved with the high-K+UW solution. The high-Na+version of the UW solution appears equally or slightly more effective for 48-hr organ preservation than the original high-K+UW solution. The use of a high-Na+UW solution reduces the problems of hyperkalemic cardiac arrest in in situ flushing of the donor for multiple organ harvesting and in transplantation of the liver. Thus, with this solution livers do not need to be flushed with a low K+-containing solution prior to transplantation.