The authors report 38 cases of patients with antinuclear antibodies directed against the centromere of the chromosomes. These were 32 cases of scleroderma, 2 cases of Raynaud's syndrome, 2 cases of rheumatoid arthritis, 1 case of polymyositis and 1 case of disseminated lupus erythematosus. In the cases of scleroderma, anti-centromere antibodies were detected in 54 p. cent of cases of Crest syndrome, for which they are a good laboratory marker; they were found more rarely in case of sclerodactyly (26 p. cent of cases) and acrosclerosis (14 p. cent of cases) and not at all in cases of localized scleroderma, diffuse scleroderma or eosinophilic fasciitis. Anti-centromere antibodies may be the only antinuclear antibodies in these patients. They can be detected using rapidly dividing cell cultures.