Slow flow in angiographically normal coronary arteries is not a rarely seen problem. It is unknown whether it is related with conduction disorders. In this study we investigated the frequency of conduction disorders in patients with normal coronary artery and slow flow. The study included 36 (22 female; mean age 63 11 years) patients who have normal coronary arteries and slow flow in coronary angiography. Patients' 12-lead electrocardiograms were analyzed for the presence of bundle branch block. Twenty-two of 36 patients (61%) demonstrated left bundle branch block. Twelve patients (33%) had normal intraventricular conduction. Only 2 of 36 patients (6%) had right bundle branch block. Microvascular disease has been implicated in coronary slow flow. However, according to the results of this study there is a close association between especially left bundle branch block and coronary slow flow. A causal relation should be sought between them with future studies.