Between January 1988 and May 1991 intravenous ganciclovir (GCV) treatment was administered to eight male AIDS-patients with unilateral cytomegalovirus (CMV)-retinitis. Despite of continuous therapy with at least the recommended dose of GCV, three patients developed slowly progressive CMV-retinitis in the fellow eye after 4 to 13 months. The progression could not be stopped by GCV and thus bilateral blindness resulted after 12 to 22 months. The number of CD4-lymphocytes in the blood was reduced in all patients, but particularly in patients with progressive disease. Treatment failure was partly related to the duration of CMV-retinitis and partly to the degree of immunodeficiency. Intravenous treatment with GCV alone can not stop the progression of CMV-retinitis in long-term survivors and in those with advanced immunodeficiency.