Groups of 25 inseminated Wistar rats each were treated daily orally by gavage with Triethylphosphat formulated in demineralised water from day 6 to day 15 p.c. in doses of O, 25, 125, or 625 agfkg body weight, respectively. The fetuses were delivered by cesarian section on the 20th day of gestation. The dams of the 625 ngfkg group revealed clinical signs like bloody mouth, staggering gait and ventral posture. The staggering gait and the ventral posture are considered to be a sign of the narcotic efficacy of Triethylphospat. Body weight gain (day 6 - 15 p.c.), feed intake day 6 - 11 p.e. and accordingly the reces excretion were weduced in the 625 mg/kg group. The intrauterine development was not affected by the treatment including external, visceral and skeletal examination of the fetuses. A teratogenic potential was not evident.