Systemic sclerosis is a connective tissue disease of unknown etiology characterized by microvascular injury and excessive fibrosis of the skin and viscera. In the United States, 5,000 to 10,000 new cases are diagnosed annually. Approximately 80 percent of these persons will eventually develop some degree of lung involvement, and restrictive lung disease (interstitial fibrosis) is now the leading cause of morbidity and mortality in systemic sclerosis. An inflammatory alveolitis is thought to be the precursor of interstitial pulmonary fibrosis in systemic sclerosis. An effective treatment for SSc interstitial lung disease has yet to be identified. Cyclophosphamide (CYC) is already being widely used by rheumatologists desperate to do something to halt rapidly declining lung function in SSC patients. Thus, the time is ripe to perform a placebo-controlled trial of CYC in this disease.