Background. In kidney transplant recipients with positive serology (R+) for the cytomegalovirus (CMV), 2 strategies are used to prevent infection, whose respective advantages over the other are still debated. This study aimed to evaluate the cost-effectiveness and cost utility of antiviral prophylaxis against CMV versus preemptive therapy, considering CMV infection-free survival over the first year posttransplantation as the main clinical outcome. Methods. Clinical, laboratory, and economic data were collected from 186 kidney transplant patients CMV (R+) included in the cohort study (85 patients who benefited from CMV prophylaxis and 101 from preemptive therapy). Costs were calculated from the hospital perspective and quality-adjusted life years (QALYs) using the EQ5D form. Using nonparametric bootstrapping, the incremental cost-effectiveness ratio (ICER) and cost utility were estimated (euros) for each case of infection avoided and each QALY gained for 1 y, respectively. Results. Prophylaxis significantly decreased the risk of CMV infection over the first year posttransplantation (hazard ratio 0.22, 95% confidence interval = 0.12-0.37, P < 0.01). Compared with preemptive therapy, prophylaxis saved financial resources (€1155 per patient) and was more effective (0.42 infection avoided per patient), resulting in an ICER = €2769 per infection avoided. Prophylaxis resulted in a net gain of 0.046 in QALYs per patient and dominated over preemptive therapy with €1422 cost-saving for 1 QALY gained. Conclusions. This study shows that CMV prophylaxis, although considered as a more expensive strategy, is more cost-effective than preemptive therapy for the prevention of CMV infections in renal transplant patients. Prophylaxis had a positive effect on quality of life at reasonable costs and resulted in net savings for the hospital.< Réduire