The features of oscillating reactions are reviewed. By means of familiar ex
amples and simple kinetic models, the role of nonlinearity, multiplicity of
steady states and stability against perturbations is outlined first. The B
elousov-Zhabotinsky reaction is then briefly discussed as an example of hom
ogeneous-phase chemical oscillator. The occurrence of oscillations and spat
iotemporal patterns in heterogeneous catalysis is described, with particula
r attention to CO oxidation with O-2 on Pt surfaces as well as on supported
catalysts in fixed-bed reactors. (C) 1999 Elsevier Science B.V. All rights
reserved.