The purpose of this contract is to acquire immunotoxicity and myelotoxicity studies on potential AIDS therapeutics. These studies will further the understanding of the potential toxicological manifestations associated with the use of these compounds and provide useful information to ongoing as well as planned clinical trials. The contract is task-oriented as such. In Year 1 the Contractor will be responsible for the following: (a) perform the proficiency requirements as discussed in Task I (A and B below), and (b) evaluate the immuno/myelotoxicity of one potential AIDS therapeutic selected by the Project Officer as described below in Task II.A. In Years 2 and 3 of the contract, the Contractor will be responsible for the following: examine the immuno/myelotoxicity of one selected AIDS therapeutic in normal mice as described in Task II.A and in animals infected with a murine retrovirus as described in Task II.B. Additionally,at the discretion of the Project Officer, other immunosuppressive therapeutics may be substituted for the potential AIDS therapeutics.