The influence of a single dose and of long-term alcohol administration on cytogenetic processes in the oocytes of Wistar white rats was studied. It is shown that a single dose of alcohol in preovulatory period when the oocytes are in the stage of diakinesismeiosis metaphase I significantly increases the rate of aneuploid gametes and dominant lethality. Analogous effect follows after long-term alcohol administration. Similarity of cytogenetic effects of acute and chronic alcohol intoxication suggests that both types of influence trigger common mechanism which results in chromosome abnormalities and, consequently, in embryonic death, i.e. dominant lethality. Taking into account that alcohol-like colchicine disturbs normal functioning of the spindle filaments, the appearance of pathology under alcohol intoxication may well be induced by disorders occurring in the stage of cell formation.