Difficulty negotiating obstacles may contribute to the high falls rate following stroke. This study examined the impact of stroke on balance during obstacle crossing. Centre of mass (COM) and centre of pressure (COP) were measured as 12 stroke subjects and 12 unimpaired subjects stepped over a 4 cm high obstacle at self-selected speed. Unimpaired subjects also walked at speeds matched to their yoked stroke subject. Compared with unimpaired subjects at matched speed, at unaffected lead toe clearance, anterior-posterior (AP) separation between COM and COP increased in stroke subjects, which might indicate instability. Step lengths before and after the obstacle tended to be reduced which could increase the risk of losing balance forwards. The COM AP velocity was reduced at affected lead toe off following stroke, which may minimise instability. Following stroke the COM and COP were positioned more posteriorly during affected lead toe clearance, which might also assist stability.