Since the last Medical Letter article on this subject (volume 25, page 54, 1983), transplantation of various organs has become routine, but problems of supply and demand have persisted. The United Network for Organ Sharing (UNOS), which has contracted with the federal government to maintain a list of patients waiting for transplantation and a registry of patients who have received an organ, reports that 18,251 patients received an organ transplant in 1994, and as of June 1995 more than 40,000 patients were waiting for one.