It has been established that the microcirculation guides the autonomic regulation of skin temperature. The effects of venous hypertension on the microcirculation may result in disturbance of autonomic regulation, leading to the development of skin disorders from a local increase in temperature. The aim of this clinical trial was to study the skin temperature of the lower extremities of patients with chronic venous insufficiency (CVI) at the different stages of the CEAP classification, and to investigate the effect on the skin temperature of administration of micronized purified flavonoid fraction (MPFF) (Daflon®). Study was made of 35 patients with CVI (24 females and 11 males with a mean age of 62.0±9.1 years). The CVI of these patients was classified according to the 6 stages of the CEAP classification system. A control group consisting of 10 healthy adults (7 females and 3 males with a mean age of 21 years) was also investigated. The skin temperature was measured at 3 sites on the lower limb - the medial malleolus, the upper one third of the medial surface of the calf (the tibia) and the medial surface of the thigh. Skin temperature measured on the arm above the deltoid muscle was considered the reference temperature for each individual. Measurements were carried out in a climate controlled room, in the supine and the upright positions, with an interval time of 10 min. For the second phase of the study, the participants of the CVI group received oral Daflon® 500 mg twice daily and the skin temperature measurements were repeated on the 7th and 15th days of administration. An increase was detected in the skin temperature of the lower limb from the lower to the higher of the 6 stages of CVI, according to the CEAP classification system, before treatment with Daflon®. The mean skin temperature on the lower limb decreased after treatment with Daflon®, but to a lesser degree at the higher stages (5 and 6) of CVI. On treatment with Daflon®, in the upright position, the mean skin temperature at the sites οn the lower limbs decreased, although this decrease was significant only at the thigh (p=0.041). The skin temperature difference between the arm and lower limb decreased significantly with Daflon® treatment at the malleolus (p=0.047), the tibia (p=0.027) and the thigh (p=0.024). In the supine position, the mean skin temperature at the malleolus and tibia decreased, but not to a significant degree, on treatment with Daflon®. The skin temperature difference between upper and lower limbs decreased significantly on Daflon® treatment at the malleolus (p=0.050), and the thigh (p=0.041), but less at the tibia (p=0.074). This study has shown that CVI is associated with skin temperature increases in the lower limbs, in relation to the 6 different stages of the CEAP classification. Skin temperature, however, cannot be used as a parameter for evaluation of the clinical outcome. Daflon® administration appears to have a beneficial effect on the skin temperature elevation occurring in the legs of patients with CVI at the different stages of the CEAP classification, and consequently is likely to help to prevent complications, such as venous ulcers.