Fifty patients with diabetic microangiopathy were studied by laser Doppler flowmetry (measuring skin blood flow at rest) (RF) and the venoarteriolar response (VAR), by transcutaneous PO2 and PCO2 measurements, and by capillary permeability evaluation (rate of ankle swelling [RAS]). Thirty of these patients were treated for 6 months with total triterpenic fraction of Centella asiatica (TTFCA) (60 mg twice daily), a drug active on microcirculation and capillary permeability. A control group of ten patients was treated with placebo and another group of ten patients was left without treatment thus acting as a second control group. After six months there were no significant changes in the two control groups. There was a significant improvement of microcirculatory parameter in patients treated with TTFCA. RF (abnormally increased at the beginning of the treatment) decreased, and the VAR (impaired at the beginning of the study) improved. PO2 increased and PCO2 decreased the abnormally increased capillary permeability was also improved (decreased). According to these data, TTFCA is useful in diabetic microangiopathy by improving microcirculation and decreasing capillary permeability. Also TTFCA protects against the deterioration of microcirculation due to diabetic microangiopathy.