Thermal decomposition of urea, and aqueous urea solutions, in the presence of 18 wt % nickel on alumina was studied by thermogravimetric analysis. A range of evolved gas species (a wider range than reported previously) were monitored by mass spectroscopy, with the evolved gases also analysed using FTIR. Results supported previous evidence of major urea decomposition starting ca. 133 degrees C, though a previously unreported two stage evolution was detected by MS in the first episode. For aqueous urea solutions, at temperatures from 80 degrees C, evolution of nitrogen was observed, along with a simultaneous release of some NH3 and what was considered to be H-2 (by the detection of a m/z = 2 ion). Activity of nickel alumina catalyst for H-2 steam reforming could not be discerned by this method, though its influence was apparent by differing evolution profiles of HCN, and NH3 in comparison to uncatalysed samples. (c) 2013 The Authors. Published by Elsevier B.V. All rights reserved.