Sixty patients with Crohn's disease have been assessed radiologically and by quantitative sacroiliac scintigraphy for evidence of sacroilitis and/or ankylosing spondylitis. The incidence of radiologic sacroiliitis (11%) and ankylosing spondylitis (5%) was no greater in our series than previously reported. However, the incidence of increased uptake of radiotracer at the sacroiliac joints was 52%. There was no correlation in the group as a whole between radiologic and/or scintigraphic evidence of sacroiliitis and the tissue antigen HLA-B27.