The aim of this study was to evaluate the variations of blood flow velocity in the skin microcirculation before and after vasoactive drugs' administration. Eight patients affected by progressive systemic sclerosis have been treated with synthesis prostacyclin for six hours during a period of fifteen days at the standard dosage of 0.5-2 ng/kg/min. We used computerized dynamic capillaroscopy with Capiflow technique to evaluate cutaneous microcirculation before and after the treatment. The Capiflow technique is a new videophotometric technique to study and quantify the diameter, density and velocity blood flow in the nutritional skin capillary. The quantitative analysis of blood flow velocity detected an increase, statistically significant, at the end of the treatment. The statistic analysis was performed by "t Student" test.