Objective The authors investigated saliva as a potentially reliable medium for estradiol (E2) measurements in postmenopausal women. The goal of this study was to determine whether or not saliva could be used in studies of postmenopausal women in place of serum samples. Specifically, the authors wondered whether or not saliva and serum E2, obtained simultaneously from samples collected from postmenopausal women, would correlate. Design Samples of saliva and serum were collected simultaneously from 43 postmenopausal women. 31 were regular users of estrogen therapy (ET), 12 used no ET. Pearson's correlation coefficients were conducted to determine the degree of relationship between saliva and serum samples among ET users and non-users. Results Among ET users saliva and serum E2 levels were significantly and positively correlated ( r = 0.81, p < 0.0001). The two E2 values were not significantly correlated among ET non-users ( r = 0.32, p < 0.31). Conclusions These data suggest that saliva E2 may be a fairly robust predictor of serum E2, but only among postmenopausal women who use ET.