A randomized open-label phase 2 trial compared the virological and clinical effects on cytomegalovirus (CMV) infection of a 14-day course of intravenous foscarnet (100 mg/[kg x 12 h]) or no treatment in 42 HIV-infected patients with < 100 CD4 cells/mm3 and persistent asymptomatic CMV viremia. All CMV markers (blood culture, pp65 antigenemia, plasma and leukocyte DNA) either became negative or decreased significantly at day 14 in the foscarnet group. CMV blood culture results at day 14 were positive in 14% of those receiving foscarnet versus 60% of control patients (P = .004). However, after the end of treatment, all markers reappeared or the virus load rapidly increased. The probability of CMV disease at 6 months was 43% in both groups. Patients who had or who achieved a negative blood culture at any time had a reduced risk of CMV disease (RR = 2.64; 95% CI = 1.24-5.62; P = .02). This study suggests that sequential courses of intravenous foscarnet might not be a good strategy for preemptive therapy in this population and that in patients with a positive blood marker, treatment able to induce and maintain negative CMV blood cultures could constitute an effective intervention.