The objective of the study was to determine the presence or levels of antibodies (Abs) against caspase-3 and their clinical relevance in systemic sclerosis (SSc). Anti-caspase-3 Ab was examined by enzyme-linked immunosorbent assay and immunoblotting. IgG anti-caspase-3 Ab levels in SSc patients were higher than in normal controls. SSc patients positive for IgG anti-caspase-3 Ab had significantly longer disease duration, more frequent presence of decreased %VC and %DLco, and elevated levels of serum immunoglobulin and erythrocyte sedimentation rates. IgG anti-caspase-3 Ab levels correlated positively with serum IgG levels, renal vascular resistance, and serum levels of 8-isoprostane. Immunoblotting analysis confirmed the presence of anti-caspase-3 Ab in sera from SSc patients. Caspase-3 enzymatic activity was inhibited by IgG isolated from SSc sera containing IgG anti-caspase-3 Ab. These results suggest that autoantibody against caspase-3 is generated in SSc and that this Ab is related to the severity of pulmonary fibrosis, vascular damage, and inflammation.