BACKGROUND: Diastolic counterpulsation has been used to provide circulatory augmentation for chronic heart failure or for short-term cardiac support. Recently an extra-aortic balloon (EAB) counterpulsation device has been proposed. AIM: To compare the circulatory effects of counterpulsation using the EAB or an intra-aortic balloon (IAB) in the acute pig model. METHODS: In six anaesthetized great white pigs (paced at 100 bpm), ECG, arterial and central venous pressures, flow in the coronary circulation and descending thoracic aorta were measured. Baseline data was collected, then with the EAB or an IAB fitted using 1:1 and 1:2 counterpulsation modes. Baseline data was compared to EAB and IAB data in 1:1 mode. Assisted beat data compared to unassisted beat data was also analysed in 1:2 mode. RESULTS: Both devices augmented peak diastolic arterial pressure, and decreased afterload. EAB counterpulsation increased diastolic coronary flow in both the 1:1 mode by 69 (p <0.05) and in the 1:2 mode by 63 (assisted versus unassisted beat, p <0.05). The IAB significantly increased diastolic coronary flow only in the 1:2 mode by 28 (p <0.01). Both devices augmented total coronary flow and some augmentation of aortic flow was observed. CONCLUSION: The circulatory effect of the EAB and IAB counterpulsation were comparable. This suggests the EAB could be used as a non-blood contacting heart assist device in patients suffering moderate-severe heart failure.