An electrocardiographic study of the effects of prenatal exposure to ethylene-glycol-monomethyl-ether (109864) (EGME) was conducted in rats. Pregnant Sprague-Dawley-rats were gavaged with 25, 50, or 100mg/kg EGME on days seven to 13 of gestation. On day 20 the dams were killed and the uteri were opened and examined for implantation sites, resorptions, and live and dead fetuses. The live fetuses were removed with their placentas and electrocardiograms were recorded. The placentas were then detached and the fetuses were weighed and examined for cardiovascular defects. All fetuses were resorbed in dams given 100mg/kg EGME. The number of implantation sites and live fetuses tended to decrease with increasing dose in the other groups. Fetal weight was slightly, nonsignificantly decreased by 25 and 50mg/kg EGME. EGME caused a dose dependent increase in fetal cardiovascular malformations, primarily ventricular septal defects and right ductus arteriosus. EGME caused a dose related increase in fetal electrocardiographic abnormalities. A prolonged QRS interval was the most common abnormality. Seven of 12 fetuses in the 50mg/kg group with abnormal QRS intervals had QRS durations of at least 40 milliseconds. Three of seven fetuses in the 25mg/kg group with abnormal QRS intervals had QRS durations longer than 39 milliseconds. Only one control fetus had a QRS interval longer than 39 milliseconds. One 50mg/kg fetus had SA block and one 25mg/kg and one control fetus had atrial flutter. Only four fetuses with prolonged QRS intervals had cardiovascular abnormalities. Four fetuses with cardiovascular abnormalities had normal electrocardiograms. The authors conclude that electrocardiography of fetuses exposed prenatally to EGME has detected a functional defect, prolonged QRS interval, that occurs more frequently than any physical malformation.