This project plan is for the supplemental support of chemistry activities of the toxicology contractors as well as to provide chemistry support for the staff research activities of the Chemical Carcinogenesis Branch. The resources of the chemistry support contractor will be used to: 1) procure difficult to obtain test chemicals prior to issuance of a Request For Proposals to ensure that a toxicology study can be conducted; 2) provide special handling of the bulk chemicals such as purification or particle size reduction that may be needed prior to use in dose formulations; 3) identify low level impurities that may have an impact on the evaluation of the carcinogenesis study results; 4) generate information for some test chemicals to assist in study design such as stability in the proposed dose vehicle or the maximum concentration in the vehicle that can be achieved; 5) evaluate and resolve analytical problems encountered by the toxicology contractors and 6) provide chemistry support for in-house studies including analysis of test article or metabolites in tissues or biological fluids.