Despite the well-known association between diabetes and sexual dysfunction, there is a lack of prospective, controlled data on the course of illness of diabetes-induced sexual dysfunction, in either male or female diabetics. Look AHEAD is one of the largest NIH-funded studies to date, with 5,000 patients at 16 clinical sites throughout the U.S.; it is a prospective investigation of the effects of weight loss and exercise, compared to a support and education group, on a broad set of biomedical and psychosocial outcomes. We are currently conducting a sub-study ("Look AHEAD Sexual Dysfunction Sub-Study"), which has been funded (DK 60438) for baseline and year I data collection. The current proposal is to continue data collection from years 2 to 4, at which time all participants will receive a comprehensive follow-up assessment, including cardiovascular, lipid, exercise and psychological measures. We propose to include additional blood samples for sex steroid hormones and a self-report assessment of sexual function to participants in the sub-study (N=+650). We have recruited at or above our projected rate (See Figure 1), and anticipate sufficient power to test the main study hypotheses. Changes in sexual function will be correlated with sex steroid hormone changes, as well as other psychosocial outcomes (e.g., depression scores). Data for the sub-study will be collected at five study sites (Miriam Hospital, Univ. Tennessee, Univ. Alabama, U. Penn, Johns Hopkins) during the 2nd, 3rd, and 4th years of the Look AHEAD trial. Participants are about equally divided between men and women, and include approximately 30% minority persons. Specific questions to be addressed are: (i) The prevalence and risk relationship of sexual problems will be evaluated through year 4, particularly the association between sexual functioning and other health characteristics (e.g. baseline BMI, hemoglobin A1c, fitness level). (ii)The principal hypothesis is that male and female patients in the Look AHEAD weight loss/special intervention condition will have improved sexual function compared to controls. Secondary analyses will examine the relationships between sexual functioning and changes in BMI, fitness level, improved glycemic control, and sex hormone alterations associated with the weight loss intervention. (iii) Finally, the proposed sub-study will investigate the relationship between changes in sexual function and quality of life outcomes.