11-beta-hydroxysteroid dehydrogenase type I (11-beta-HSD1) in the white adipose tissue (WAT) of rats catalyses the conversion of 11-dehydrocorticosterone to corticosterone, a more active glucocorticosteroid. Glucocorticosteroids in WAT stimulate adipocytes differentiation and increase adipocytes size. The aim of this study was to examine the association between expression of 11-beta-HSD1 in the WAT of male and female rats and adipose tissue mass as well as body mass.Perirenal WAT from male and female Wistar rats aged three months, and ovariectomized females of the same age, was used in the study. 11-beta-HSD1 gene expression was assayed in the perirenal WAT of rats by real-time PCR.11-beta-HSD1 gene expression in the perirenal WAT of male rats was higher than in female rats. The WAT and body mass of male rats was also higher than in females. 11-beta-HSD1 gene expression in the perirenal WAT as well as WAT mass and body mass increased simultaneously after ovariectomy.The results presented in this paper suggest that higher 11betaHSD1 gene expression in the WAT is associated with higher body and adipose tissue mass. Moreover, our results suggest that oestradiol can modulate 11-beta-HSD1 gene expression in the WAT of rats.