The overall objectives of this study are: A. to design and validate a dietary data collection instrument for use in a chemoprevention trial which is self-administered, specific to the nutrient(s) of interest (in this case vitamins A and C), and specific to the dietary patterns of the study population (80 young adult women in Tucson, Arizona). Our specific approach includes: 1. for each subject: collectionof 8 independent days of dietary records; and administration of two usual food intake questionnaires (NCI) Core dietary questionnaire and Tucson questionnaire) which differ somewhat in format and content; 2. validation of results from diet records against questionnaire, with particular attention to total vitamin A & C intake, foods designated, and portion sizes; 3. development of final questionnaire based on #2, and validation and assessment with 20 additional subjects drawn from same population; 4. development of compact data base for analyzing final questionnaire; 5. development of protocols for a) revising the questionnaire to cover other nutrients and/or study populations and b) maintaining quality control on questionnaire data in a longitudinal study. B. to explore the relationships among plasma nutrient levels (retinol, beta-carotene, vitamin C), intake on the day preceding blood sample, and usual intake as estimated from usual intake questionnaires and mean of 8 dietary records. Results will suggest 1) whether estimates of nutrient stores can be improved by determining preceding day's diet, and 2) the implications of using a single plasma nutrient level determination in studies of cancer risk factors.