Male or female subjects between the ages of 18 years and 65 years will be selected for the study if they have a clinical diagnosis of Raynaud's phenomenon secondary to systemic sclerosis (scleroderma) despite being on vasodilator therapy. Raynaud's phenomenon is defined as a history of cold sensitivity associated with colour changes of cyanosis or pallor. Patients with a history of at least 4 attacks per week during two-week pre-trial period even with treatment with other vasodilators will be recruited. Patients fulfilling the diagnostic criteria of scleroderma (as per American College of Rheumatology criteria) or having presence of at least 3 of the 5 features of the CREST syndrome (calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasias)will be invited to participate in the study.