Pneumocystis pneumonia is a major cause of death for AIDS patients. Few therapeutic agents are available. Those that are available are toxic and often ineffective. These laboratories have developed unique techniques to study enzyme systems in the organism and to screen the effectiveness of various drugs against these enzymes. The techniques involve sophisticated, but labor intensive process for obtaining the organism and screening large numbers of drugs against the target enzymes. The importance of this project is the identification of new agents against pneumocystis pneumonia that might be more potent and less toxic.