Two efforts are underway to enhance the comparability between trials conducted by the Division and ensure the collection of data on important variables in a standardized way. The first, a core questionnaire, is not intended to be exhaustive, but rather to provide a core which each investigation will expand upon. It includes demographic and tracking data, and exposure data including smoking, diet, occupation and psychosocial factors. The development of the areas of investigation and wording of specific questions made use of prior standardization projects and large national surveys. Thus, most questions included in the core data have been subjected to pretesting and will permit comparability of results with representative national data. Second, a dietary assessment questionnaire is being developed for inclusion in the core data to be collected by DRCCA intervention trials, as well as in other diet investigations. The aim is to develop a questionnaire appropriate for large-scale administration and valid for individual, as opposed to group, dietary intake. The method involves a quantitative food frequence questionnaire, in which the list of foods is based on the 200,000 food items reported by the 20,000 individuals examined in NHANES II. The validity of the instrument will be examined in a separate validation study, and a biochemical validation is also planned. In addition, earlier work developed a list of indicator foods for vitamin A assessment, using a similar approach. Further work on this instrument will refine the list of foods and examine its validity and ability to classify individuals with respect to their vitamin A intake. It is expected that the collection of a set of baseline data in an identical manner will imiprove the interpretation of results from different studies, facilitate the resolution of conflicting data, and thereby enhance the contribution of each study to knowledge about prevention strategies.