In this paper, we employ the Taguchi method to optimise our newly developed time-modulated chemical vapour deposition (TMCVD) process. TMCVD can be used to deposit smoother, nanocrystalline diamond (NCD) coatings onto a range of substrate materials. The implementation of the Taguchi method to optimise the TMCVD process can effectively save valuable time, considerable effort and money, this being the major advantage of the method. The Taguchi method significantly reduces the number of experiments required to optimise a fabrication process. In this study, we investigate the effect of five TMCVD process parameters on five key factors of the as-grown samples. Each parameter was varied at four different values (experimental levels). The 5 considered parameters, taking into consideration the experimental levels, were optimised after performing only 16 experiments. The as-grown films were characterised for hardness, quality, surface roughness and microstructure using SEM, Raman spectroscopy, surface profilometry and Vickers hardness testing. (C) 2004 Elsevier B.V. All rights reserved.