Cytomegalovirus retinitis, the major cause of blindness in patients with the acquired immunodeficiency syndrome, can be arrested by early detection and treatment. We identified 9 screening indices for early CMV retinitis: T-4/T-8 ratio less than 0.11, T-4 count less than 30, T-8 count less than 500, leukocytes less than 4,200, platelets less than 240,000, hemoglobin less than 11.6, hematocrit less than 35, less than 6 for a diagnostic profile which incorporates these 7 indices, and less than 2 for the IA-sum which compounds T-cell inversion and anemia. A threshold value was determined for each index, identified by retrospective review of charts of 15 patients with CMV retinitis and 30 without. Sensitivity, specificity, positive predictive value, negative predictive value, and receiver operating characteristic curve area was calculated. The best screening index was the T-cell ratio, which had the highest sensitivity (0.93), negative predictive value (0.94-0.99) and receiver operating characteristic curve area (0.89), and a positive predictive value among the highest (0.50-0.82).