Antinuclear and/or antinucleolar antibodies were demonstrated in the sera of 74 of 76 patients (97%) with progressive systemic sclerosis, using tissue culture cells (HEp-2) as substrate in the indirect immunofluorescent method. Six patterns of nuclear staining and three nucleolar patterns were recognized. The nuclear patterns were centromere, fine speckles, coarse speckles, diffusely grainy, homogeneous and nuclear dots. The nucleolar patterns were speckled, homogeneous and clumpy. The results of digestion studies with ribonuclease, deoxyribonuclease and trypsin suggested that the nuclear antigens are proteins, some of which may be associated with chromatin. The nucleolar antigens appeared to be nucleic acid in nature. Certain characteristic serologic and clinical features associated with staining patterns were observed. The diffusely grainy pattern was seen only in sera containing antibody to Scl-70 antigen. Centromere staining was confirmed to be highly selective for the CREST (Calcinosis, Raynaud's phenomenon, esophageal involvement, sclerodactyly and telangiectasis) variant of progressive systemic sclerosis with rheumatoid factor titres higher in these patients with anti-centromere antibodies.