Patients are assigned to one of two groups: (1) Patients with any retinitis in zone 1 or patients with retinitis involving 25 percent or more of zones 2 and 3; and (2) Patients in whom retinitis is confined to less than 25 percent of zones 2 and 3 of the retina. Half the patients in group 1 get immediate treatment with ganciclovir; the other half receive immediate treatment with foscarnet. Patients in group 2 are treated with foscarnet or ganciclovir either immediately or treatment is deferred. If patients in group 2 have strong preferences regarding when therapy is instituted, they may elect immediate treatment or deferral of treatment.