The results of a series of 32 rat liver transplants are described to analyze the efficacy of components of UW solution. Rat livers were stored at 4°C in standard UW solution or one of three simplified variants for 24 hr prior to orthopic liver transplantation. In standard UW solution (solution A) the one-week survival rate was 3 of 8. Using solution B, which differs from solution A in the omission of hydroxyethyl starch and adenosine, the one-week survival rate was 2 of 8. Solution C, a further-simplified version of solution B with omission of allopurinol, Bactrim, and insulin, gave a one-week survival rate of 3 of 8. Solution D is identical to solution B except that the sodium and potassium concentrations are reversed. Using this solution, 5 of 8 rats survived more than one week.We conclude that the effectiveness of UW solution is maintained in a substantially simplified form, and that solution D, with the Na/K ratio reversed to give a high Na variant, may improve survival.