An automatic computer generated Pacemaker Diagnostic Diagram described previously (PACE 8:691) was plotted below the ECG to aid the diagnosis of complex pacemaker‐heart interaction. During routine followup visits, 14 patients with Symbios 7005 or 7006 DDD pacemakers were studied during various temporary programming protocols to demonstrate common and unusual pacemaker problems. The examples discussed in this paper explain how the side‐by‐side ECG and diagram synergistically aid human diagnosis of undersensing, oversensing, loss of capture in either or both chambers, upper rate limiting, safety pacing and atrial arrhythmias. The Pacemaker Diagnostic Diagram was a useful clinical too! especially for analysis of complex pacemaker arrhyt