The authors have collected 19 cases of ankylosing spondylitis with an alteration of intracardiac conduction. The lesions are usually situated high in the bundle of His, as shown by successive electrocardiograms and endocavitary studies. Progression by regressive acute episodes and the response to anti-inflammatory agents suggests that the disorder of conduction is inflammatory in origin. Syncopal attacks are rare (1 case out of 19) and a pacemaker is rarely indicated. Almost half the patients had aortic insufficiency, one patient had tricuspid stenosis and two patients had heart failure in the absence of any valvular lesion. The associated ankylosing spondylitis is characterised by the severity of the inflammatory signs (average sedimentation rate 50 mm in the first hour) and by the extent of peripheral articular involvement and extra-rheumatological manifestations. Almost one in two patients had iritis, with the same proportion applying to a past history of Reiters syndrome.