This work was undertaken to examine possible embryotoxicity of Ruta graveolens (rue), a plant used by indigenous communities for the purposes of therapeutic and fertility regulation. Superovulated mice were mated and isolated after copulation. They were given aqueous extract of R. graveolens (5, 10, and 20% w/v) or plain water (control) orally for 4 days. Ninety-eight hours post-human chorionic gonadotrophin (hCG), embryos were flushed from oviducts and uterine horns to assess their state of development and extent of embryo transport. Ingestion of rue at 10 and 20% resulted in a high proportion of abnormal embryos (36.7 and 63.6%, respectively, P < 0.05). Cell number was diminished (P < 0.01) and embryo transport was slightly delayed in the highest dose group. These findings demonstrate that oral administration of R. graveolens extract can interfere with preimplantation development and embryo transport. © 2003 Elsevier Inc. All rights reserved.