To elucidate further the clinical significance of the anticentromere antibody (ACA), 32 Australian-born Caucasian patients with scleroderma (SD) or CREST (calcinosis, Raynaud's phenomenon, oesophageal dysmotility, sclerodactyly and telangiectasia) were reclassified as ACA-positive (19 patients) or ACA-negative (13 patients). The clinical features of the two groups were compared. Mean disease duration was 11.7 years for the ACA-positive group and 1.1 years for the ACA-negative group. No ACA-positive patient had generalized skin SD, whereas all ACA-negative patients with disease duration greater than 6 months had moderate or severe proximal scleroderma. Only one ACA-positive patient had serious extra-oesophageal internal organ involvement, excluding primary biliary cirrhosis (three patients) which is itself associated with ACA. Three ACA-negative patients had serious extra-oesophageal internal organ involvement. No ACA-positive patient had been treated with penicillamine or captopril compared with 11 ACA-negative patients. Thus ACA appears to be a favourable prognostic indicator. Analysis of individual CREST manifestations in ACA-positive patients revealed that most had 'incomplete CREST', lacking one or two of the five features. The classification of SD patients as ACA-positive or ACA-negative is suggested.