Fibroblast heterogeneity has been the basis of a pathogenetic theory of scleroderma in which one subpopulation of high collagen producing cells is expanded by selective growth. In studies by others using gingival cells, fibroblast membrane Clq receptor affinity correlates positively with collagen production. We have demonstrated distinctly higher amounts of Clq binding of fibroblasts from 2 patients with early scleroderma compared to late scleroderma and controls. These observations are consistent with the overgrowth of a normally occurring subpopulation of cells and provide support for clonal selection in the pathogenesis of scleroderma.