Small-angle X-ray scattering measurements have been made on six fractions of bisphenol A polycarbonate with weight-average molecular weights M-w of 2.3 X 10(3)-1.3 X 10(4) in tetrahydrofuran at 25 degrees C using a new type of apparatus equipped with an imaging plate detector. The z-average radii of gyration < S-2 >(1/2)(z) and the particle scattering functions obtained are analysed on the basis of current theories for the worm-like chain, along with previous data for < S-2 > (from light scattering on high molecular weight samples) and the intrinsic viscosity [eta]. Excluded-volume effects on < S-2 > (z) and [eta], which are significant for M-w above 10(4), are taken into account by the quasi-two-parameter (QTP) theory for the worm-like or helical worm-like chain. It is found from the analysis that all the properties examined are explained consistently by the worm-like chain whose contour is characterized by a Kuhn segment length of 3.0 nm and a linear mass density of 240 nm(-1). In particular, the theory of Yoshizaki et al. for [eta] of an unperturbed worm-like chain combined with the QTP theory is found to describe the molecular weight dependence of Flory＇s viscosity factor over the entire range of M-w examined, i.e. from 2.3 x 10(3) to 4.7 x 10(5).