JP-8 aviation fuel is being phased in as a replacement for both JP-4 and JP-5 jet fuels presently in use by the Air Force and Navy, respectively. At the present time, 11% of active-duty Air Force personnel are women of child-bearing age. This study was undertaken to determine the threat posed to the unborn fetus should female active-duty personnel come in contact with JP-8 while pregnant. Time-mated Sprague-Dawley rats were dosed orally with JP-8 at 0, 500, 1000, 1500 and 2000 mg kg-1 day-1 on days 6-15 of pregnancy. The number and type of fetal malformations and variations observed did not differ significantly between dose groups. Dams in the 1000, 1500 and 2000 mg kg-1 day-1 groups gained significantly less body weight during pregnancy than did control dams. Embryo toxicity was indicated by a significant reduction in fetal body weight in the 1500 and 2000 mg kg-1 day-1 dose groups.