Noting the common occurrence of arthritis in contemporary elephants, a skeletal study was undertaken to assess the frequency and nature of the affliction. Spondyloarthropathy was unequivocally diagnosed in mammoths (Mammuthus primigenius) and contemporary elephants on the basis of fusion of vertebral bodies with marginal syndesmophytes, zygoapophyseal joint fusion, and peripheral erosive arthritis and fusion and was easily distinguished from infectious spondylitis and diffuse idiopathic skeletal hyperostosis. Vertebral involvement was limited in distribution, in a pattern characteristic of human psoriatic arthritis and Reiter's syndrome, also referred to as reactive arthritis. Infectious diarrhea or sexually transmitted reactive arthritis are the most likely candidates for this phenomenon, as recognized in elephants and mammoths, which affords a unique opportunity for therapeutic intervention.