A single family is presented in which 2 of the 3 sibs and 3 of 9 first degree relatives had Crohn's disease. Two subjects with Crohn's disease had classical ankylosing spondylitis (AS), and HLA typing revealed HLA B27 in all 5 members of the immediate family. The value of quantitative sacroiliac scintigraphy (QSS) in clinical practice is demonstrated. Both patients with AS had evidence of currently active sacroiliac disease in association with radiological change. One symptomatic sib had QSS evidence of sacroiliitis without radiological abnormality.