Juvenile ankylosing spondylitis (JAS) is a chronic inflammatory arthritis of the peripheral and axial skeleton, frequently accompanied by enthesitis. About four percent of patients with JAS have ulcerative colitis or Crohn's disease. Crohn's disease is the more common of the two and is diagnosed in 26 percent of patients with chronic spondyloarthropathy. In this paper, a 14-year-old male patient is presented as a typical case of juvenile ankylosing spondylitis and Crohn's disease with low back pain, morning stiffness, limited motion in anterior and lateral flexion and extension, left sacroiliitis, ankylosis in the apophyseal joints of the lumbar vertebrae, abdominal pain, bloody diarrhea, characteristic histopathologic changes of colonic involvement such as lymphoid follicles, fissures, submucosal polymorphonuclear cell infiltration and definite ganglion cells. The current therapy with mesalazin, having fewer side effects than sulfosalazin, and its applicability in combination with naproxen sodium is also discussed.