Epidemiological studies suggest that consumption of isoflavones rich diets can improve several postmenopausal complications. The aim of this study was to investigate the absorption and the efficacy of isoflavonic supplementation in the treatment of menopausal symptoms.36 postmenopausal women received 75 mg/day of isoflavones in the form of tablets, for six months. 21 subjects concluded the treatment. Plasmatic and urinary samples were collected before and after the treatment, along with a dietary interview. Isoflavones were determined in biological samples and in commercial administered supplements by a HPLC/DAD system.Results showed the presence of genistein (from 0.043 to 1.820 micromol/L) in plasma samples, and of genistein (from 2.486 to 20.363 micromol/24h) and daidzein (from 11.106 to 98.091 micromol/24h) in the urines of the treated women. In the 21 completers the Greene Climateric scale value for hot flushes changed from 3 to 1 or 0. No changes of the endometrial thickness and of the breast tissue were detected. The analysis of the supplement content in the tablets was in agreement with what declared by the producer.Administration of isoflavone supplements produced a decrease of symptoms in this cohort of postmenopausal women monitored for isoflavone absorption.