Initial clinical findings are reported for the 3339 young women enrolled in the Diethylstilbestrol Adenosis (DESAD) project. Changes in the vaginal mucosa (VEC--vaginal epithelial changes), which were detected by colposcopy or iodine staining, occurred in 34% of 1275 participants identified by review of prenatal records 59% of participants who themselves requested entry into the project, and 65% of participants referred by a physician. Analysis of data on the 298 women who were identified by record review and whose prenatal records contained complete information about drug exposure indicated that VEC is most closely associated with the timing of the onset of intrauterine exposure to diethylstilbestrol (DES), total dose, and length of exposure. Frequency of VEC was also found to decrease with age. No instances of severe dysplasia, carcinoma in situ, invasive squamous cell adenocarcinoma, or clear cell carcinoma were observed among the women identified by record review.