Four samples of hyaluronan in the sodium form, ranging in weight-average molecular weight, M-w, from 6.67 x 10(5) to 4.23 x 10(6) were investigated by asymmetrical-flow field-flow fractionation coupled to multiangle light scattering (FIFFF-MALS) in 0.2 M aqueous NaCl at 25 degreesC. M-w and z-average radii of gyration, R-Gz, obtained via FIFFF-MALS showed a good agreement with the results obtained by conventional static light scattering. Furthermore, the molecular weight dependence of the radius of gyration for sodium hyaluronan obtained via FIFFF-MALS was analyzed on the basis of the Kratky-Porod model for unperturbed wormlike chains combined with the Yamakawa theory for radius expansion factor, and a sufficiently good agreement was observed between the theoretical prediction and experimental data. These results show the potential usage of FIFFF-MALS regarding size separation and molecular characterization even for weakly stiff chains.