Cytomegalovirus (CMV) infection is the most frequent infectious complication observed in renal-transplant recipients and induces a significant morbidity in these patients due to CMV disease itself and to associated renal dysfunction or opportunistic superinfection. In order to evaluate the effect of gangiclovir prophylaxis we conducted an open-label prospective randomized study of ganciclovir administration in CMV seronegative recipients of a renal allograft from CMV seropositive donors. Ganciclovir (5 mg/kg b.i.d./day for 14 days) was started on day 14 after transplantation. Thirty-two patients were included in this study (15 in the control group, 17 in the ganciclovir group). There was no significant difference between the two groups for age, immunosuppressive regimen, number of rejection, steroid pulses, and OKT3 treatments. Renal and patient outcomes were similar in both groups. The rate of CMV infection and CMV disease were similar in both groups (80% and 73.3% in the control group versus 70.6% and 47.1% in the ganciclovir group; P = NS). Less severe CMV disease was observed in the ganciclovir group compared to controls. The delay between transplantation and CMV infection was significantly longer in the ganciclovir group compared to control group (68.1 +/- 5.1 versus 44.0 +/- 5.2 days, P < 0.005). Twelve group patients (80%) versus nine (53%) of the ganciclovir group required curative treatment with ganciclovir after the diagnosis of CMV infection (NS). All the patients recovered from CMV disease and no significant side effect was observed during ganciclovir administration.(ABSTRACT TRUNCATED AT 250 WORDS)