This is a research study of an investigational product called Mycophenolate mofetil (MMF). The study is designed to establish the safety and potential benefit of MMF. MMF has proven one of the most effective medications to date for SLE and associated nephritis. It also appears to be active in polymyositis and dermatomyositis. This medication inhibits inosine monophosphate dehydrogenase, the rate-limiting enzyme in synthesis of guanosine nucleotides. It blocks the type II isoform found in activated lymphocytes more potently than the type I isoform inhibiting both T- and B-lymphocytes. In SSc, MMF has been tried after anti-thymocyte globulin in one small open label study with efficacy with a significant improvement in skin score. We will test the safety and efficacy of MMF in SSc. All study patients will receive the study medication. The effect of the study medication will be examined in two subgroups of patients: those with early or progressive skin disease (skin substudy) and those with muscle disease (muscle substudy). The change in modified Rodnan skin score (MRSS) and creatinine phosphokinase (CK) for, respectively, the skin and muscle substudies at 6 months after treatment will be compared to baseline values.