1. First cadaver-donor recipients had a 7% death rate if the kidney originated from a CMV+ donor compared with 5% if the kidney came from a CMV-donor. This 2% difference was highly significant (p < 0.001). Graft survival rates were correspondingly 2-3% lower as a result of deaths. 2. This same trend was noted in the 1991-1993 period as in the 1988-1990 period. 3. Increased incidence of deaths in D+/R+ transplants was most frequently statistically significant when patients were divided by early function. 4. Death rates in diabetics rose from 7% in D-/R- combinations to 13% in D+/R- patients (p < 0.001). Patients with other diseases did not show as marked an effect. 5. Among kidneys from living-related donors, there was no noticeable effect of donor CMV status. Thus, for these donors, no precautions need be taken regarding CMV status. Spousal-donor transplants had a higher graft survival if a D-/R- rather than other combinations were used. 6. The incidence of CMV positivity was slightly higher in Black patients compared with Caucasians, in females compared with males, and increased progressively with age. CMV positivity increased in patients with multiple grafts, presumably because transplanted patients increased in CMV positivity. Among patients who were on dialysis, the CMV positivity was higher than in donors of cadaver organs. There was a substantial difference in CMV positivity in different areas of the country, ranging from 36% in Ohio to 65% in Washington. 7. The HLA matching effect was greater than the CMV effect, justifying its use as the main prospective factor in kidney allocation. CMV prophylaxis is needed for patients receiving kidneys from CMV+ donors. The data indicate that, whenever possible, CMV+ donor kidneys should not be used for CMV- IDDM patients.