Fifty-eight patients with Raynaud's syndrome who had no evidence of definite underlying connective tissue disease had serum analyzed for the presence of anticentromere antibody using indirect immunofluorescence techniques on HEp-2 cell lines. Eighteen patients (31 percent) were anticentromere antibody-positive. The anticentromere antibody-positive group demonstrated significantly more frequent digital telangiectases, digital edema, elevated levels of immunoglobulins, and low C4 values. Photoplethysmography revealed significantly diminished blood flow in the anticentromere antibody-positive group. Capillary microscopy revealed significantly increased avascularity and number of dilated loops in the anticentromere antibody-positive group. Giant loops were seen exclusively in the anticentromere antibody-positive group. The clinical findings in the anticentromere antibody-positive group are suggestive of a transition to a connective tissue disease with features of the CREST syndrome.