Objective To examine the association between polarity of atrial premature complexes (APCs) and stroke.Design A prospective study.Setting and participants A total of 11 092 participants in the Jichi Medical School cohort study were included after excluding patients with atrial fibrillation. We analysed stroke events in patients with (n=136) and without (n=10 956) APCs. With regard to polarity of APCs, patients were subcategorised into having (1) negative (n=39) or non-negative (n=97) P waves in augmented vector right (aVR), and (2) positive (n=28) or non-positive (n=108) P waves in augmented vector left (aVL).Outcome measures The primary endpoint was stroke.Results Patients with APCs were significantly older than those without APCs (64.1±9.2 vs 55.1±11.6 years, p