The objective of this study was to evaluate the efficacy of flaxseed meal and flaxseed extract in reducing climacteric symptoms of menopausal women. Ninety menopausal women were randomly distributed into three study groups: group I received 1 g per day of flaxseed extract containing at least 100 mg of secoisolariciresinol diglucoside (SDG), group II received 90 g per day of flaxseed meal containing at least 270 mg of SDG, and group III received 1 g per day of collagen (placebo group). Subjects were assessed for menopausal symptoms by the Kupperman index at the beginning and at the end of the 6 months of treatment. Subjects were also assessed for endometrial thickness and vaginal cytology. The Kupperman index values at the beginning and end of the treatments were analyzed using the paired t-test. Both the flaxseed extract (P=.007) and the flaxseed meal (P=.005) were effective in reducing the menopausal symptoms when compared with the placebo control (P=.082). Alternatively, the changes in Kupperman index were also computed and submitted to analysis of variance. In this case, no significant differences were found (P=.084) although the data indicate a decreasing tendency for the Kupperman index by both the flaxseed extract and the flaxseed meal groups. Neither the flaxseed extract nor the flaxseed meal exerted clinically important estrogenic effects on the vaginal epithelium or endometrium as revealed by the absence of changes in the blood levels of follicle stimulating hormone and estradiol, as well as in the endometrial thickness, and vaginal epithelial maturation value. No serious adverse events related to the treatments were reported. Although the results of the present study do not allow an unequivocal conclusion about the action of flaxseed on the menopausal symptoms, they suggest that it could be premature to conclude that no such action exists. Clearly the matter still deserves further experimental attention.