There have been profound changes in the pattern of cytomegalovirus (CMV) retinitis over the last two decades. The epidemiology and behaviour of CMV retinitis has been significantly altered by Acquired Immune Deficiency Syndrome (AIDS). It was uncommon prior to the AIDS epidemic, but soon became the most common retinal infection in AIDS patients. In the past several years, highly active anti-retroviral treatment (HAART) has achieved a dramatic improvement in the prognosis for patients infected with human immunodeficiency virus (HIV). As a result, HIV patients are living longer and have a reduced risk of CMV retinitis. Some patients with CMV retinitis who respond to HAART develop a transient symptomatic vitritis while others undergo no reactivation of their retinitis despite having no specific anti-CMV therapy. This pattern is likely to undergo further change as the treatment of HIV and CMV disease continues to improve.