Advances in the field of antiviral therapy are now occurring with increasing frequency and rapidity and often generate varying degrees of confusion among those of us whose practices are focused primarily on therapy with antibacterial agents. How to treat cytomegalovirus infections in patients infected with the human immunodeficiency virus constitutes one of the best examples of the quandaries engendered by these advances, and the topic is reviewed in this first AIDS Commentary update. Given the U.S. Food and Drug Administration's recent approval of foscarnet, this discussion is very timely; it is particularly relevant for clinicians to be made aware of current lines of thought regarding induction versus maintenance therapy, the benefits of efficacy versus adverse effects of drug-related toxicity, and the interactions between antiretroviral drugs and ganciclovir or foscarnet. Dr. W. Lawrence Drew's career in this area has been long-standing and productive, and he is one of the leading experts in the field. In this update he addresses these perplexing issues.