A retrospective study of all patients diagnosed as having obstructive pulmonary disease (POD), who were admitted to our department during 1989, was carried out. The presence of cardiac arrhythmia (CA) in standard ECG having been correlated to clinical and laboratory parameters on admission. Out ot 101 admissions, 67.3% had a type of CA, the most frequent being sinus tachycardia (54.4%). 71.9% of the patients who had cardio-respiratory decompensation, 72.8% of those admitted in basal situation III/IV and 86% who were regularly taking theophylline (p less than 0.01), had a type of CA. Our data suggests that patients with worst functional situation and those with cardiorespiratory decompensation had a higher incidence of CA and that regular theophylline intake can play a role in the etiopathogenesis of CA.