Objective — to study the role of polymorphism of biotransformation genes of xenobiotics of the second phase in the features of metabolism and cellular energy exchange in women of reproductive age and in perimenopause. Material and methods. Two groups of women were examined: I (control) group — 25 women of reproductive age (25.7±3.8 years); II (main) — 25 women in perimenopause (48.9±3.4 years). DNA isolated from peripheral blood leukocytes. Biochemical examination of serum of venous blood is performed on an automated analyzer with the help of unified test systems. The activity of enzymes of cellular energy exchange of succinate dehydrogenase (SDH) and a-glycerophosphate (a-GPDH) dehydrogenase in lymphocytes was determined by the cytochemical method followed by visual morphometry. Results. In carriers of allele GSTP1 I105V G serum content of the main metabolites (glucose, cholesterol, triglycerides, uric acid) is significantly higher, and the activity of mitochondrial enzymes in the blood lymphocytes significantly lower than their peers normosthenic with variant allele GSTP1 A the same gene. Conclusion. As a result of the study, the effect of GSTP1 I105V A>G polymorphism on metabolic changes leading to the development of overweight and obesity in postmenopausal women was established.