Using a developed laser light-scattering (LLS) procedure, we accomplished the characterization of an unfractionated polyimide (UPI) in CHCl3 at 25 degreesC. The Laplace inversion of precisely measured intensity-intensity time correlation function from dynamic LLS leads us first to an estimate of the characteristic line-width distribution G(T), and then to the translational diffusion coefficient distribution G(D). By using a previously established calibration of D (cm(2)/s) = 3.53 x 10(-4) M-0.579, we were able to convert G(D) into a molecular weight distribution. The weight-average molecular weight M,, calculated from the molecular weight distribution, agrees well with that directly measured in static LLS. Our results indicate that both the calibration and LLS procedure used in this study are ready to be applied as a routine method fur the characterization of the molecular weight distribution of polyimide.