In 1969 we described a method for kidney preservation that used a brief flush with a new "intracellular" solution followed by ice storage. This paper stimulated research into optimizing solution composition culminating in the UW solution which is now the accepted standard. Further developments in the design of solutions for hypothermic organ preservation have proceeded along several paths, including: (1) modification and simplification of UW solution, (2) investigation of organ specific requirements, (3) addition of pharmacologic agents particularly calcium antagonists to flush solutions, (4) the concept of "microperfusion" for control of acidosis, (5) the use of solutions containing polyethylene glycol, and (6) the use of a terminal rinse solution. Broadly speaking, the results of these studies have shown that it is possible to improve upon the UW solution by simplification, eliminating several of the components, and that sodium variants, and pharmacological additives, such as chlorpromazine, may yield better results in experimental and clinical trials. It has also been found that there are special requirements for individual organs, rendering the concept of a universal solution unlikely. Of the promising new ideas, microperfusion and polyethylene glycol have been found to be very effective for heart preservation yielding for the first time virtually perfect 24-hour preservation. The concept of a terminal rinse to diminish reperfusion injury has strong experimental support and awaits clinical evaluation.