When negotiating irregular surfaces, the control of dynamic stability is challenged. In this study, we compared the adjustments in stepping behaviour and arm-swing of 18 unilateral transtibial amputees and 17 able-bodied participants when walking on flat and irregular surfaces. Experimental findings revealed that unilateral transtibial amputees reduced their gait velocity only slightly when walking on irregular surfaces. Analyses of the temporal gait characteristics, i.e. stride time, stance time, double-support time and step frequency, showed no statistically significant adjustments. Interestingly, the amputees did not increase the stability margins for lateral balance which were calculated based on the concept of the "extrapolated center of mass". Furthermore, they did not increase their step width, which was already wide when walking on the flat surface. However, amputees did increase the lateral component of relative arm-swing velocity in order to walk stable on irregular surfaces. (C) 2010 Elsevier B.V. All rights reserved.