Recent advances in soft ionization techniques for mass spectrometry of polymeric materials make it possible to determine the mass of intact molecular ions exceeding 1 x 10(6) Da. Developments in high resolution mass spectrometers have additionally led to impressive advances in our ability to characterize polymers. The entire molecular mass distribution of a polymer sample can be accurately measured. From the molecular mass, the molecular formulae and information regarding polymer composition and end-groups can be deduced. The two techniques which have received the most attention are matrix-assisted laser desorption/ionization and electrospray ionization. In recent work, these techniques have been combined with chromatographic separations, and a series of mass spectra are acquired for each fraction of the distribution. This simplifies the analysis by reducing the number of components present in each mass spectrum, and additionally improves quantitation.