Microchimerism is defined by the presence within an individual of a low level of cells derived from a different individual. The main, natural source of microchimerism is pregnancy. The migration of fetal cells into maternal blood during pregnancy has become an accepted fact. The maternal cells can also be found in the fetal circulation. Recent studies indicate that cells can persist in the maternal circulation for years after pregnancy. Maternal cells can also persist in het progeny. The autoimmune diseases are a diverse group of disorders. Many of them are of unknown etiology. Women are disproportionately affected by autoimmune disease and the incidence of some autoimmune disease in women peak following childbearing years. The integration of observation from differing fields of medicine has led to the consideration that microchimerism may be involved in the pathogenesis of some autoimmune diseases. Early results offer support for a potential role of microchimerism in SSc. The aim of this paper is to present current knowledge about this problem.