Female Sprague-Dawley (CD) rats were exposed to 2450-MHz(CW) microwave radiation at incident power densities of 0 or 28 mW/sq cm for 100 min daily on the 6th through 15th day of gestation. The whole-body specific absorption rate at 28 mW/sq cm is estimated to be 4.2 W/kg. These exposure conditions raised rats' average colonic temperatures to 40.3C at the end of irradiation. There were 67 sham-irradiated and 70 microwave-irradiated females. When these groups were compared, no significant differences were found in pregnancy rates; in the numbers of live, dead, or total fetuses; in the incidences of external, visceral, or skeletal anomalies or variations; or in the body weight of live fetuses. It is concluded that these conditions do not have an effect on the gross structure of the fetal rat when applied repetitively during post-implantation pregnancy. It is also strongly suspected that this lack of an effect may hold true at any exposure level less than that which will kill a significant number of the dams by hyperthermia (colonic temperature > 40C).