The human retroviruses, HTLV-I and HIV, are playing clinically important roles in a variety of ocular disorders, particularly in uveitis. Both viruses are integrated in the genome of infected T cells. HIV-I infection causes the death of the infected T cells, thereby affecting the host defence system and causing AIDS. Subsequent opportunistic infections of ocular tissues, such as CMV retinitis, are a serious problem in clinical ophthalmology all over the world. Another human retrovirus, HTLV-I, has been known as the causative agent of T cell malignancies (ATL and T cell lymphoma) and chronic myelopathy (HAM/TSP), and is now recognised as a causative agent for a specific type of intraocular inflammation characterised by vitreous opacities with mild iritis and mild retinal vasculitis (HTLV-I uveitis). The mechanism by which HTLV-I causes uveitis is still unknown, but our recent data suggest that it is most probably an immune mediated mechanism by activated CD4 T cells infected with the virus. HTLV-I uveitis, therefore, may implicate a significant role of retroviruses in autoimmune diseases and further the pathogenesis of diseases with infection/autoimmune overlap.