The paper presents the results of evaluating the effect of genetically modified (GM) maize on the prenatal and postnatal development of rat progeny in three generations. An experiment used 280 adult rats (160 females and 120 males) and 1545 infant rats of the first month of life. The animals were divided into 2 groups: 1) those given a diet including GM maize (an experimental group); 2) those fed on its isogenic control (a control group). The maize was included into the diet in maximally possible amount that did not impair the balance of essential nutrients (31.4% caloric value). Analysis of the data obtained from studies of the prenatal (preimplantation and postimplantation death and fetal somatometric parameters) and postnatal (physical development, survival, changes in somatometric parameters) development of rat offspring revealed no effect of GM maize as compared to the isogenic control. All the parameters were in the normal physiological range typical of the animals of this species and age. Thus, dietary intake of the given amount of GM maize had no impact on rat progeny development.