Chemical wave patterns in catalytic CO oxidation on a Pt(110) surface have been studied in the 10(-5) mbar range using low energy electron microscopy (LEEM) as spatially resolving method. During rate oscillations a cellular pattern develops whose characteristic dimensions are apparently determined by the surface topography of the Pt(110) surface. Exposure to oscillatory conditions causes a roughening of the surface associated with macroscopic changes in the surface topography. (C) 2004 Elsevier B.V. All rights reserved.