A high prevalence of antibodies to cytoskeleton components (anti-CYTO) and of anti-smooth muscle (SMA) and antinuclear (ANA) antibodies has been found in inflammatory bowel disease (IBD). In particular, a significant correlation has been documented between anti-CYTO and activity of the disease in ulcerative colitis and anti-fibroblast intermediate filaments (anti-vimentin) antibodies and Crohn's disease. The antibodies are detectable in the three major immunoglobulin classes, including IgA. While titres of anti-CYTO did not exceed 1:40, ANA and SMA were of high titres (up to 1:1,280). Antibodies to epithelial cells intermediate filaments (anti-cytokeratin) were detected only occasionally. The significance of these findings in IBD is discussed.