The method of preparation and methods of analysis of a narrow distribution polystyrene of ∼7 ku used in an interlaboratory comparison of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) of synthetic polymers is described. Size exclusion chromatography was used to measure the polystyrene sample variability. Fourier transform infrared spectroscopy and MALDI-TOF-MS were used to analyze end groups on the polymer. The polystyrene was analyzed by MALDI-TOF-MS and classical methods of polymer characterization. The number (Mn) and mass (Mw) average of the molecular mass distribution (MMD) determined by the classical methods (light scattering and NMR) were compared with those obtained by MALDI-TOF-MS. Agreement between classical methods to obtain the moments of the MMD and the MALDI is found to be good overall. However, all the experimental values obtained by MALDI fell below the classical values. A discussion of why these values are lower is included. We discuss the stat...