Dr. Wafaa el-Sadr of Harlem Hospital, reported on the behalf of the Community Programs for Clinical Research on AIDS and the AIDS Clinical Trials Group about the use of Atovaquone (A) versus Dapsone (D) in the prevention of PCP for patients intolerant to trimetheoprim-Sulfa. The study randomized 1,057 patients with a median CD4 of 60 cells/mm3 to either 1500 mg of A suspension, or 100mg of D/ day. There were 121 cases of first time PCP in the A group versus 134 in the D group (NS), 4 cases of cerebral toxoplasmosis in the A group and 3 in the D group (NS), and 232 deaths in the A group and 137 in the D group (NS). The rates of adverse events with discontinuations in both groups were comparable -- 133 in A and 137 in D. However, specific adverse events differed in that GI symptoms including diarrhea were more common in the A group, but hypersensitivity reactions and anemia were more common with D. The results suggested that although the overall efficacy, and tolerability rates for A and D were comparable, trimetheoprim-sulfa patients who were already on Dapsone and tolerating it should stay on it, but that patients who had no prior experience with either drug, were more likely to tolerate Atovaquone as the next line PCP prophylactic agent.