To facilitate provision of atovaquone (566C80) to patients who have severe Pneumocystis carinii pneumonia (PCP) and are intolerant and/or unresponsive to trimethoprim / sulfamethoxazole ( TMX / SMX ); to monitor serious adverse events attributable to 566C80.

Inclusion Criteria

Patients must have the following:

• Clinical diagnosis of acute severe Pneumocystis carinii pneumonia (PCP).
• Dose-limiting intolerance to TMP / SMX and parenteral pentamidine.
• Willingness and ability to give informed consent.

Exclusion Criteria

Co-existing Condition:

Excluded:

• Patients with a history of intolerance to 566C80. Patients with the following prior conditions are excluded: History of serious dose-limiting adverse experience during previous 566C80 therapy, thought to be attributable to the drug.

Required:

• Trimethoprim / sulfamethoxazole (TMP/SMX); pentamidine.