Current therapies to treat opportunistic infections associated with the Acquired Immunodeficiency Syndrome (AIDS) are highly toxic, extremely expensive or marginally effective. Because present therapies for certain infections produce toxic reactions in a large percentage of patients, the availability of alternative therapeutics are of utmost importance. Since these infections produce significant morbidity and mortality in patients with AIDS, the National Institute of Allergy and Infectious Diseases (NIAID) has funded several programs to facilitate drug development efforts against opportunistic infections by providing contract resources for efficacy evaluations in animals, a critical component in new drug approval. The availability of animal model testing systems will provide the NIAID with testing capabilities to evaluate therapies for treatment against Pneumocystis carinii, both singly and in combination as well as determine the pharmacokinetics and toxicities of the experimental therapies. This will permit the submission of the resulting data in support of an IND application for the new therapy. The contractor will have the capability to evaluate therapeutic agents in small animal (in vivo) and culture (in vitro) model test systems, develop alternative protocols to accommodate special characteristics of individual therapies of model test systems, measure general toxicity, determine pharmacokinetic parameters, etc, to assist the sponsor in the development of new therapies against P. carinii.