Thirty-nine children with a syndrome of seronegative enthesopathy and arthropathy were evaluated. The group included 25 patients with no apparent underlying primary disease and 13 with either ankylosing spondylitis, inflammatory bowel disease, reactive arthritis, or Reiter's syndrome. Significant distinguishing characteristics of the group included male predominance, late age at onset, positive family histories of arthritis, oligoarthropathy, axial skeleton involvement, and the presence of the B27 histocompatibility antigen. This syndrome is distinguishable from other childhood rheumatic disorders, including juvenile rheumatoid arthritis. Its recognition may reliably identify children with the prodromal manifestations of seronegative spondylarthropathies.