Current therapies to treat some of the opportunistic infections associated with the Acquired Immunodeficiency Syndrome (AIDS) either are toxic, marginally effective and/or inexpensive. In addition, there is no therapy recognized as effective for certain of the pathogens. Since these infections produce significant morbidity in patients with AIDS, the National Institute of Allergy and Infectious Diseases has funded several programs to facilitate discovery and development of novel therapies for the treatment of AIDS-related opportunistic infections. Due to the limited patient population affected by some of these opportunistic infections, the NIAID has funded a series of drug development contracts to complement the drug discovery process. Currently contracts are in place for chemical resynthesis, analytical chemistry/quality control and pharmaceutical manufacturing. The Government lacks the central resources to provide the health and safety assessment for these newly developed therapies as required by the Food and Drug Administration prior to initial testing in humans. This resource will provide the NIAID with testing capabilities to determine, in both rodents and larger animals, the toxicity of single and multiple doses of experimental therapies under conditions that will permit submission of the resulting data in support of an IND application for the new therapy. The contractor will carry out these studies in accord with FDA's Good Laboratory Practice regulations. The contractor will also have the capability to carry out studies in the areas of specific organ toxicity, dose ranging toxicity studies, pharmacokinetics, etc., to assist the sponsor in addressing key toxicity questions in the development of a compound.