The relationship between retinal microangiopathy and some features of human immunodeficiency virus (HIV) infection such as HIV antigenemia, antibodies to the viral proteins, T lymphocyte subsets, were studied in 71 patients with acquired immunodeficiency syndrome (AIDS). The absence of antibodies to the HIV p24 protein was significantly related to retinal microangiopathy (p = 0.0051) and more closely to retinal cotton-wool spots (p = 0.0007); the combination of positive antigenemia with the absence of antibodies to p24, which is typical of the later phases of HIV infection, was found in a larger percentage of patients with cotton-wool spots (p = 0.0013) than in subjects with every sign of microangiopathy (p = 0.0546). T-helper (CD4+) cells count below 200 cells/mm3 was also detected in a higher percentage of patients with HIV-related retinal microangiopathy (p = 0.009). These findings suggest that retinal microangiopathy and especially retinal cotton-wool spots are related to the progression of immunodeficiency.