AbstractWomen exposed prenatally to diethylstibestrol (DES) develop a variety of reproductive tract anomalies. Most of these anomalies have been replicated in strain CD‐1 mice after similar DES exposure. Recently, impaired reproductive performance in DES‐exposed women has been reported. To see whether the mouse model also replicates this defect, at study of reproduction was performed. Pregnant CD‐1 mice were injected with DES and their female offspring were raised to breeding age. The latter were then exposed continuously to untreated males for a maximum of 4 months. Among 74 mated mice, 34 became pregnant and 11 of these pregnancies ended in abortion or stillbirth. Other anomalies encountered were: two fetuses with compressed heads, one of which seemed blocked from delivery by a vaginal adenocarcinoma; two uterine tumors, one of which was a teratocarcinoma; two teratomas located in uterine lumina; and two uteri containing placentas without embryos. Since the frequency of successful pregnancies in the DES‐exposed mice was reduced below control levels to a degree similar to that reported for DES‐exposed women, the validity of the mouse model has been confirmed for this chara