Cytomegalovirus (CMV) is a non-pathogenic organism in the immunocompetent, but is a major cause of morbidity and mortality amongst patients with AIDS, and the retina is the commonest site of infection. If left untreated, patients with CMVR will develop disease in their second eye and ultimately become blind. However, with correct diagnosis and treatment useful vision can be maintained in the majority of cases. Fifteen to 20% of patients with AIDS will contract cytomegalovirus retinitis (CMVR) and this may be the AIDS-defining diagnosis though more commonly it occurs months after the diagnosis of AIDS. Given the increasing number of HIV positive patients and their longer survival, it is likely that CMVR will become an increasingly prevalent condition. In these patients loss of sight from CMVR has devastating consequences in terms of loss of independence and quality of life and therefore ophthalmologists and physicians should be aware of the presenting characteristics of CMVR, be familiar with therapy and its complications, and be able to recognize relapsing infection.