Free-radical polymerizations of styrene (S) and methyl methacrylate (MMA) in bulk were induced at 25 and 60 degrees C using a pulsed ultraviolet excimer laser. Molecular weight distributions (MWDs) of the polymer products produced were measured by both size exclusion chromatography and matrix-assisted laser desorption/ionization mass spectrometry and compared with one another. Propagation rate coefficients k, were determined from these MWDs taking into account impacts of varying termination rates and varying pulse periods as well as errors resulting from instrumental broadening. Values of k(p)(25 degrees C, S) = 96.5 L mol(-1) s(-1), k(p)(60 degrees C, S)= 364 L mol(-1) s(-1), k(p)(25 degrees C, MMA) = 372 L mol(-1) s(-1), and k(p)(60 degrees C, MMA) = 962 L mol(-1) s(-1) are finally suggested.