Three-hundred-and-thirteen back pain sufferers completed a screening questionnaire for inflammatory back pain. This was positive in 46 (15%), who were invited for a further examination. Only two of these patients had definite ankylosing spondylitis. Eighteen of them (39%) had other features associated with spondyloarthropathy. It is suggested that up to 5% of back pain sufferers may have a mild form of ankylosing spondylitis that may never progress to definite ankylosis, but for whom treatment as if they had ankylosing spondylitis may be of benefit.