The presence of ESRD was ascertained through reports by the donors and recipients themselves. In December 2003, after November 1963 we initiated a comprehensive effort to get hold of all persons who had donated a kidney. We consulted phone and internet web directories and asked recipients because of their specific donor’s contact information. We asked the donors we located to supply us with updates on their health status and to report the results, if available, of urinalysis and serum creatinine testing. At the beginning of this work in 2003, we produced lists of donors who had been regarded as alive and stratified them according to sex and the number of years since donation .