Participants underwent an initial baseline screening, including the collection of physical measurements, blood specimens, an inventory of medications and supplements, and completion of questionnaires pertaining to medical history, family history, reproductive history, lifestyle and behavioral factors, and quality of life. In addition, more specific information was collected with regard to the participant's geographic residence history, passive (i.e., "second-hand") smoking exposure in childhood and adulthood, early life exposures, details of physical activity, weight and weight-cycling history, and occupational exposures. In addition to the baseline data collected, OS participants received annual questionnaire mailings to update selected exposures and outcomes, and were expected to make an additional clinic visit, to include an additional blood collection, about three years post-enrollment. It was planned that participants would be followed for an average of 9 years.