Core component C1 will provide analytical services for projects 1 and 3. The services will consist of: a) assays for 13-cis retinoic acid, retinyl palmitate, and beta-carotene b) assays of serum cotinine and c) long term storage of serum aliquots for any future testing, as may be required. Quantitation of the micronutrients in serum will be performed with high performance liquid chromatography (HPLC). The HPLC technique will be validated by assessment of accuracy, precision, and recovery. Method reliability will be insured with the use of quality assurance serum pools obtained from the National Institutes of Standards and Technology (formerly NBS) and with standard quality control procedures. Serum cotinine will be assayed by using a commercially available immunoassay. The long term storage of serum aliquots will be performed at -70 degrees C. Laboratory data will be transmitted to the Biostatistics Data Management - M.D. Anderson Cancer Center Core