C57BL/6J mice were used to study the ocular teratogenic effects of cyclophosphamide administered to pregnant females on d 9 of pregnancy at a dose of 5 mg/kg body weight. Nile blue staining demonstrated increased cell death at the base of the optic stalk, in the optic vesicle, and in the perivesicular mesenchyme in treated embryos. Malformations studied at gestational d 11 and 16 by light and scanning electron microscopy included microphthalmos, microphakia, and aphakia and were predictable based upon patterns of increased cell death. These anomalies are similar to those reported with exposure to ethanol or isotretinoin on gestational d 7.