This study used rats bred at the Petrov Research Institute of Oncology. On the 21st day of pregnancy N-nitrosomethylurea (NMU) (20 mg/kg) was administered to the animals intraperitoneally. From the 7th day of pregnancy experimental rats were treated with 10% glucose solution instead of drinking water, and during 1.5 months after delivery the rats of this group and their progeny received 5% glucose solution. The present work has revealed an increase of fetal weight in pregnant rats treated with glucose. A significant increase of tumor frequency was detected in the progeny of these rats. In the male progeny, tumors of the nervous system and kidneys, typical for NMU, predominated and in females, tumors of other organs and tissues, particularly the mammary gland, pituitary body and hemopoietic system, predominated. This paper discusses a possible mechanism of the modifying effect of glucose on transplacental carcinogenic action of NMU.