We examined 42 patients with the acquired immune deficiency syndrome: 11 of these had retinal lesions. In this study we reported five cases; all were examined within several weeks of admission to the Maggiore Hospital, and at various intervals thereafter. Ophthalmic evaluation included determination of visual acuity, slit-lamp examinations, direct ophthalmoscopy with the pupil dilated, fundus photography and fluorescein angiography. Peripheral blood mononuclear cells were isolated during gradient density centrifugation. Lymphocyte subsets were determined by immunofluorescence with monoclonal antibodies of the OKT series. All patients demonstrated a reduction of the ratio of T-helper to T-suppressor. Patient no. 1 was a 41 year-old hemophiliac man became ill (ARC) in June 1986; initially the patient had no ocular lesions. After five months developed bilateral retinal cotton wool spots. The patient's clinical conditions progressively worsened during the ensuing months and after fifteen months he felt a decreased vision in left eye: retinal examination disclosed a presumed CMV retinitis. Patient no. 2 was a 30 year-old intravenous drug-user man. At the time of the admission (AIDS) ophthalmologic evaluation revealed multiple cotton wool spots in both eyes. These changed of number and size during the following months. This patient was treated with ganciclovir (dihydroxy propoxymethyl guanine) because developed a CMV encephalopathy. We noted after this treatment a strong reduction of the cotton wool spots without an improvement of the general conditions and he died a month later. Patient no. 3 was a 26 year-old drug-user woman admitted for ARC. Ophthalmologic evaluation disclosed in right eye a presumed CMV retinitis with vascular sheathing and hemorrhages, and in left eye a little white retinal lesion (an initial retinitis) and cotton wool spots. The general and the retinal conditions rapidly worsened and she died three months later. Patient no. 4 was a 24 year-old women, intravenous drug-user, admitted for AIDS complicated by central nervous system infection by Toxoplasmic Gondii. Ocular examination revealed in right eye retinal cotton wool spots, and in left eye a white chorioretinal lesion with vitritis attributed to Toxoplasma Gondii. This retinochoroiditis improved after empiric therapy with sulfonamides and pyrimethamine. Patient no. 5 was a 37 year-old bisexual man admitted for AIDS. The findings on ophthalmologic examination were: CMV retinitis in right eye and retinal cotton wool spots in left eye. Treatment with ganciclovir resulted in an improvement of general symptoms.(ABSTRACT TRUNCATED AT 400 WORDS)