During chronic venous insufficiency (CVI), microcirculatory changes, e.g. a decrease in transcutaneous oxygen pressure (tcpO2) and an increase in transcutaneous carbon dioxide pressure (tcpCO2), are implicated in the pathophysiology of trophic disorders leading ultimately to venous ulcers. Daflon 500 mg1, a micronized purified flavonoid fraction, has been shown to improve venous tone, capillary permeability and resistance, and lymphagogue activity at a daily dose of tablets. To assess the effects of Daflon 500 mg on microcirculatory parameters by means of laser Doppler fluxmetry and transcutaneous oxymetry, a 3-month, double-blind, randomized, parallel-group study was carried out in 104 patients divided into 3 groups according to the daily dose: 1 tablet (group 1 n = 34), 2 tablets (group 2, n = 33), on 4 tablets (group 3, n = 37). All patients (mean age 43.7 ± 13.1 years; 100 females, 4 males) included in the study were affected by mild CVI. They were followed for 90 days with visits at 1 month (day 28) and months (day 90). At inclusion, there were no significant differences between groups as regards biometric data, mean tcpO2 (group 1, 62.7 ± 4.5 mm Hg; group 2, 64.0 ± 3.3 mm Hg; group 3, 64.1 ± 3.5 mm Hg), mean tcpCO2 (group 1, 40.7 ± 2.5 mm Hg; group 2, 39.3 ± 2.9 mm Hg; group 3, 40.0 ± 2.5 mm Hg) and laser Doppler parameters. Fourteen patients withdrew from the study (group 1, n = 4; group 2, n = 3; group 3, n = 7): 9 for reasons not related to treatment, 3 for adverse events, 2 because they were lost to follow-up. From day 0 to day 90, mean tcpO2 significantly increased (p 2 significantly decreased (p