EXPOSURE of women to diethylstilbestrol in utero has been linked to the development of adenosis and clear cell adenocarcinoma of the vagina.<sup>1,2</sup>A variety of male genital tract abnormalities, including epididymal cysts, maldescended testes, hypoplastic testes, varicoceles, and spermatozoal defects, occur with increased incidence in men exposed to diethylstilbestrol in utero.<sup>3,4</sup>Testicular tumors occur in adult mice given diethylstilbestrol,<sup>5</sup>and preneoplastic testicular changes have been described in mice exposed prenatally to diethylstilbestrol.<sup>6</sup>The possibility of carcinogenesis has been suggested in diethylstilbestrol-exposed males,<sup>3,4</sup>but, to our knowledge, until now no case of testicular cancer has been documented in a person exposed in utero to diethylstilbestrol. We report a seminoma and ipsilateral epididymal cysts in a 28-year-old man with known diethylstilbestrol exposure. <h3>Report of a Case</h3> A 28-year-old man was first seen with a large, painless scrotal mass that had slowly developed during one year. Antenatally, his