To identify the incidence of pericardial effusion in patients after cardiac surgery using a hand-carried cardiac ultrasound device, 200 patients were assessed on postoperative day 3. If a pericardial effusion was found, patients were monitored for 3 consecutive days with a hand-carried cardiac ultrasound device. Within 72 hours after surgery, 43 patients (21.5%) had developed an effusion, of whom 2 patients had cardiac tamponade and 41 patients (21%) had a small pericardial effusion. No difference was found in the incidence of effusion based on the type of cardiac surgery. Of patients with a small pericardial effusion on day 3 after surgery, an additional 2 of 41 (5%) developed cardiac tamponade.