The recent finding of a distinct subset of serum neutrophil autoantibodies in the majority of patients with ulcerative colitis has been confirmed by several studies. Although autoantibodies probably have no direct role in mediating tissue damage, they may reflect the underlying immunologic disturbance that leads to the disease. The clinical importance of ulcerative colitis-linked neutrophil autoantibodies is uncertain, although they may be useful diagnostic markers. Family studies indicate that they might also be useful markers of genetic susceptibility. Future identification of the antigen or antigens recognized by these ulcerative colitis-linked autoantibodies will facilitate the development of improved assay systems and the study of the immunologic basis for their occurrence.