The persistence of enthesopathic changes was studied by ultrasound (US) in 23 patients with spondylarthropathy during a 6-month prospective trial with sulphasalazine (Salazopyrin). During the follow-up significant improvement was seen in the joint symptoms and in the laboratory variables. By US 78% of the patients had enthesopathy at entry and 74% after 6 months of follow-up. The plantar fascia was the enthesis most frequently affected. Treatment with sulphasalazine had no obvious influence on the persistence of enthesopathy. Enthesopathy is as a rule a constant phenomenon and is probably caused by chronic enthesitis. A parallel resolution of anatomic soft tissue changes and the clinical status was not seen on US. There was also no evidence of a favourable effect of sulphasalazine on enthesopathy in the 6-month follow-up.