Progressive microangiopathy and endothelial dysfunction are identified in early phases of systemic sclerosis. These alterations may result in progressive reduction of vessel lumen, decreased blood flow, and a state of chronic hypoxia resulting in digital ulcers, digital pitting, and, in more severe cases, gangrene and amputation of the extremities. Few studies aimed to evaluate the effects of Sildenafil on the microcirculatory blood flow in patients with Raynaud's phenomenon secondary to systemic sclerosis (SS). Moreover, no study has evaluated the effect of this drug on the number and function of endothelial progenitor cells in SS patients. The relatively new technique of laser Doppler imaging (LDI) allows an objective measurement of superficial cutaneous microvascular blood flow and constitutes a promising approach in the assessment of the digital microvascular vasoreactivity in response to cold stimulus or in response to treatment in SSc patients.