Both aerosolized pentamidine and dapsone have been shown to prevent PCP, but both drugs cause side effects. This study attempts to determine which drug is more efficacious as prophylaxis against PCP in patients who cannot tolerate trimethoprim/sulfamethoxazole.

Patients are evenly divided between two treatment arms to receive either aerosolized pentamidine every 4 weeks or dapsone orally three times weekly. Follow-up data is collected every 3 months, and patients are clinically evaluated every 6 months. Patients who develop PCP or a severe or persistent study drug toxicity may be switched to the alternative study drug at the clinician's discretion. Average duration of follow-up is 2 years.

Inclusion Criteria

Patients must have:

• HIV infection.
• CD4 count <= 200 cells/mm3 or <= 15 percent of total lymphocytes OR a history of prior PCP.
• History of intolerance to trimethoprim and/or sulfonamides.
• No active pneumocystosis. Patient or guardian must sign informed consent. Pregnant patients are eligible at the clinician's discretion. Patients who do not meet required laboratory values may be eligible at the discretion of the clinician.

Exclusion Criteria

Concurrent Medication:

Excluded:

• Any medication with potential anti-PCP activity.

Patients with the following prior conditions are excluded:

• Treatment-limiting reaction to pentamidine or dapsone.