Cytomegalovirus (CMV) infection is very common in acquired immmune deficiency syndrome (AIDS) with approximately 40% of patients presenting CMV visceral involvement at advanced stage disease. The most common localizations are retinitis and gastrointestinal involvement; central nervous system disorders are likely to be underestimated. Diagnosis of CMV disease should be assessed, for all localizations except retinitis, on the association of clinical symptoms with presence of CMV inclusions in biopsy specimens. Two drugs, ganciclovir and foscarnet, are currently licensed for treatment. Both are administered intravenously. Since progression of CMV disease is very common particularly in retinitis, maintenance therapy should be given throughout remaining life. Unfortunately, maintenance therapy does not entirely prevent the risk of relapses. Drug toxicity is mainly bone marrow suppression with ganciclovir and renal insufficiency with foscarnet. Since quality of life is severely impaired by long-term daily intravenous treatment, orally active drugs are urgently needed both for treatment and primary prophylaxis of CMV infection. (C) 1993 Wiley-Liss, Inc.