Objective:To document response to foscarnet salvage therapy in patients with cytomegalovirus (CMV) retinitis who are intolerant of or resistant to ganciclovir.Methods:Patients with AIDS and CMV retinitis who had documented hematologic intolerance or resistance to ganciclovir therapy received an induction course of foscarnet, 60mg/kg every 8h for 14 days, and subsequent chronic maintenance foscarnet therapy at a daily dose of 60, 90 or 120 mg/kg/day. The first 87 patients were randomly assigned to receive maintenance foscarnet at a dose of 60 or 90mg/kg/day; all subsequent patients were assigned a maintenance dose of 120 mg/kg/day.Results:A total of 156 evaluable patients were enrolled. Median time to retinitis progression and survival did not differ significantly among groups assigned to different maintenance foscarnet doses. Among patients with retinitis progression documented ophthalmologically occuring at ≤2 week intervals, despite optimal doses of ganciclovir, time to progression on foscarnet therapy was a median 8 weeks at all doses studied. By dose assignment, there were no significant differences in serious drug-associated toxicity, although trends toward increased renal and hypocalcemic adverse events were observed at higher maintenance doses.Conclusion:In patients intolerant of ganciclovir, salvage foscarnet therapy resulted in a longer time to retinitis progression than reported previously in historic controls who terminated ganciclovir therapy. In patients who exhibited clinical resistance to ganciclovir, foscarnet appeared to have efficacy in controlling retinitis. No significant differences in either efficacy or toxicity were observed in the range of foscarnet maintenance doses studied.