Near infrared spectroscopy has been used to monitor the effects of changing build parameters on the sintering process of selective laser sintering components. The surface roughness of the parts produced has been studied whilst modifying laser scan speed and laser power build parameters. Near infrared spectroscopy is shown to be a powerful tool in detecting subtle variations in the coalescence of particles that form the surface topology of the component. Principal component analysis (PCA) performed on the diffuse reflectance spectra obtained from the surface of the components shows a strong correlation between near infrared (NIR) spectra and build parameters. Using the chemometric model produced from the PCA analysis it is possible to calculate build parameters for unknown components, making NIR a useful aid for quality control of additive manufacturing technologies. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 3153-3158, 2011