Dilemmas in the prophylaxis of Pneumocystis carinii pneumonia.

: Pneumocystis carinii pneumonia has been the most common life-threatening opportunistic infection in patients with acquired immunodeficiency syndrome. With a better understanding of the natural history of HIV infection, however, we have come to realize that prophylaxis against P carinii can prevent the majority of such pneumonias. In this article, I focus on the rationale behind such prophylaxis, as well as the choices and dilemmas the clinician faces in deciding on the most appropriate therapy and when it should be instituted.