Background/Aims: Previously we have shown that administration of 150 mg of vitamin E (·-tocopherol) per day to rats having diabetes decreases the rate of embryo malformations and increases their maturation and size. The present study was addressed to determine the effects of different doses of vitamin E upon these parameters. Methods: Female rats were made diabetic (D) with streptozotocin, and from day 0 of gestation they were treated daily with 25 (D+25), 50 (D+50), 100 (D+100), 150 (D+150), and 500 (D+500) mg of vitamin E administered orally and were compared with control (C) animals. Results: On day 11.5 of gestation, crown-rump length, somite number, and protein and DNA levels were lower in D than in C embryos. Crown-rump length and somite number increased with 100 mg or higher doses of vitamin E, although the values observed in C embryos were not reached. The proportions of reabsorption and malformations were 24.7 and 50%, respectively, in D rats, and in the rats supplemented with vitamin E they decreased to 22.7 and 19% in D+25, 16.4 and 21.3% in D+50, 16.2 and 12% in D+100, 12.9 and 13.9% in D+150, and to 43.9 and 10.8% in D+500 rats, whereas the values were 6.8 and 4.9% in C animals. Conclusions: Administration of vitamin E to D rats decreases the rate of embryo malformations, dependent on the dose administered. However, high doses have a negative effect in the conceptus, as shown by the increased rate of reabsorptions in the D+500 group.