A simple one-dimensional Monte Carlo model has been developed to simulate the chemicalvapour deposition (CVD) of a diamond (100) surface. The model considers adsorption,etching/desorption, lattice incorporation, and surface migration along and across the dimerrows. The top of a step-edge is considered to have an infinite Ehrlich–Schwoebelpotential barrier, so that mobile surface species cannot migrate off the edge. Thereaction probabilities are taken from experimental or calculated literature values forstandard CVD diamond conditions. The criterion used for the critical nucleusneeded to form a new layer is considered to be two surface carbon species bondedtogether, which forms an immobile, unetchable step on the surface. This nucleus canarise from two migrating species meeting, or from direct adsorption of a carbonspecies next to a migrating species. The analysis includes film growth rate, surfaceroughness, and the evolving film morphology as a function of varying reactionprobabilities. Using standard CVD diamond parameters, the simulations reveal that asmooth film is produced with apparent step-edge growth, with growth rates (∼1 µm h−1) consistent withexperiment. The β-scission reaction was incorporated into the model, but was found to have very little effectupon growth rates or film morphology. Renucleation events believed to be due toreactive adsorbates, such as C atoms or CN groups, were modelled by creatingrandom surface defects which form another type of critical nucleus upon which tonucleate a new layer. These were found to increase the growth rate by a factor of∼10 when the conditions were such that the rate-limiting step for growth was new layerformation. For other conditions these surface defects led to layered ‘wedding cake’structures or to rough irregular surfaces resembling those seen experimentally during CVDof nanocrystalline diamond.