Introduction: Isotretinoin (RA), used for the treatment of cystic acne, is a powerful teratogen, causing craniofacial dysmorphisms and neural tube defects. We present two patients with RA embryopathy and oculomotor nerve synkinesis. Methods: Retrospective review of patient records. Results: Two patients presented with third nerve synkinesis and fetal RA exposure. Both had marked elevation of the upper eyelids on adduction such that the lid fissures alternately opened and closed on gaze from side to side. Both patients showed typical dysmorphisms of RA embryopathy. The first patient had complete agenesis of the cerebellar vermix and died at 2 years. The second patient had restricted extraocular muscles in one eye and was exotropic and hypotropic. Discussion: Both patients demonstrated simultaneous innervation of the medial rectus and levator palpebrae muscles causing coincident lid elevation in adduction. This evidence of oculomotor nerve synkinesis is consistent with animal studies showing abnormalities in the formation of cranial nerve ganglia following fetal RA exposure. Conclusion: RA is a powerful teratogen. These patients provide additional clinical evidence of its influence on neural migration during early development. Copyright © 2005 by the American Association for Pediatric Ophthalmology and Strabismus.