Gel permeation chromatography equipped with a low-angle laser light-scattering detector (GPC-LALLS) was employed to determine the M-n and M-w of any polymer system such as flexible polymers (polystyrene, PSt), rod-like polymers (poly(n-hexylisocyanate), PIC), star polymers ((PSt)(n) and [poly(alpha-methylstyrene)](4), (PalphaMSt)(4)), linear block copolymers (polystyrene-block-polyisoprene, PSt-block-PIs) and star block copolymers ((PSt)(4)-star-(PIs)(7)). For the homopolymers (PSt, PIC, (PSt)(n) and (PalphaMSt)(4)), the determined M-n(GPC-LS) and M-w(GPC-LS) values are in good agreement with the M-n(OSM) and M-w(LS) values determined by osmometry and light scattering, respectively. For the block copolymers (PSt-block-PIs and (PSt)(4)-star-(PIs)(7),) two composition distributions (CDs) have to be considered: one is a CD among the different molecular weights and the other is a CD among the same molecular weights. Block copolymers are classified into four groups from the viewpoint of a combination of the two CDs. In any group, new analytical equations for determining Mn and M, were derived by the assumption that the block copolymers, which appear at the same elution volume of the GPC chromatogram, have the same molecular GPC-LS sm weight 3. The resultant M-n BC(GPC-LS) values were in good agreement with the M-n(OSM) values. GPC-LALLS was found available for determining M-n and M-w of the block copolymers.