The shortage of cadaveric donors coupled with a rapidly growing number of potential recipients has resulted in an increased use of older donors. In 1992, 10.7% of all cadaveric kidney transplants were from donors above the age of 55 compared with 5.4% in 1988. The present investigation serves as a follow-up of a prior study of the effect of donor age on outcome with a 2-year analysis of more than 30,000 cadaveric kidney transplants performed in the United States between October 1, 1987, and December 31, 1991, that were reported to the United Network for Organ Sharing. There was no difference between the graft survival at 1 and 2 years comparing donors aged 56-65 versus 65 and older, but the older donors (aged 56 and greater) had a 1- and 2-year graft survival that was approximately 10% and 14% less than that for recipients from the ideal age group of donors (16-45 years). There was no practical adverse interaction between donor age and recipient age, gender, diabetic status, peak PRA (panel reactive antibody activity) level of mismatch, cold ischemia time, or recipient race on outcome. The kidneys from older donors had poorer graft survival than the kidneys from younger donors when transplanted into recipients of repeat transplants, though the impact of repeat transplant and donor age on graft survival are independent of one another. These data suggest that kidneys from donors over the age of 55 overall have reduced functional reserve, which has an adverse effect on long-term function. Thus, attempts should be made to better estimate functional reserve among the older age group, but age alone should not be the sole factor for exclusion of a potential donor. The use of older donors appears to present an increased but acceptable risk of graft loss 2 years after transplant.