We plan to perform a two phase study of low-dose fluconazole prophylaxis in HIV infected patients with a history of OPC. Patients with advanced immunosuppression (CD4 less than or equal to 150 cell/mm3) who have not received prior fluconazole prophylaxis will be included. Phase 1 of the study will be a placebo-controlled trial of fluconazole at a dose of 200 mg three times weekly. Phase 1 will examine whether this low-dose prophylaxis can delay recurrence of OPC. Phase 2 of the study will be an open-label prophylaxis with fluconazole at first 200mg thrice weekly, then 200mg daily as patients develop recurrent OPC. In this phase the primary question to be answered will be whether subjects starting in the placebo arm of Phase 1 will progress more or less rapidly to clinical fluconazole failure compared to those starting in the fluconazole arm. We will learn more about the natural history of fluconazole resistance, including how gradually the change occurs, how much fluconazole the patient has received at the time resistance develops and whether the resistance occurs in the patient's own isolate or from acquisition of a new isolate. Other evaluations will include compliance, cost, and host and organism-associated factors. If thrice weekly fluconazole prophylaxis can increase the time to development of resistance and decrease episodes of OPC in this group of severely immunocompromised individuals, it would increase the effective use (to include cost-effective use) of fluconazole in the treatment of OPC.