A study was made of electrocardiographic changes in 3 and 6 week old rats exposed in-utero to ethylene-glycol-monomethyl-ether (109864) (EGME) in order to determine if intraventricular conduction delays previously observed in fetuses would persist beyond the fetal/neonatal period. Pregnant female Sprague-Dawley-rats were treated by gavage with 0, 50, or 75mg/kg EGME on days seven through 13 of gestation. Surviving offspring at 3 and 6 weeks of age were assessed electrocardiographically in an unanesthetized, unrestrained condition. EGME treated dams had a prolonged gestation, smaller litter size, lower pup weight, and a lower percentage of dams that delivered. There was a dose related effect of EGME on pup survival, with 100 percent mortality after day one in the 75mg/kg group and about 50 percent mortality by day three in the 50mg/kg group. Surviving offspring in the low dose group weighed significantly less than controls at 8 weeks of age. EGME treated rats had slightly increased heart weights and significantly increased heart/body weight ratios, but no microscopic abnormalities were detected. Electrocardiographic changes included increased QRS intervals in 3 and 6 week old pups and significantly prolonged T-waves in 6 week old pups. Nonsignificant increases in QRS amplitude were observed in exposed offspring. Intraventricular conduction delay in one or more offspring was noted in 36 and 54 percent of 3 and 6 week old litters, respectively. The authors conclude that doses of EGME that are not maternally toxic have a severe effect on reproductive outcome, producing an intraventricular conduction delay that persists through at least 6 weeks of age.