The structural features of the disk-like components in the anisotropic spheres from KP pitch were investigated by molecular weight measurement, NMR and IR spectroscopy, analyses of evolved gases during heat-treatment, and reactivit'ies with phenol. A comparison was made with the corresponding properties of the isotropic quinoline insoluble matter in the pitch. m-IR spectra of KP spheres and KPQI indicate the presence of aliphatic C-H bonds, in addition to aromatic bonds in these materials. The ratios of aliphaticlaromatic hydrogen obtained by H-NMR, and evolved ethane analyses after the reductive ethylation, were larger in both cases than the value calculated by assuming that all hydrogens in the original material were aromatic, although it was rather difficult to identify the aliphatic hydrogen in further detail by these methods. By the reaction with phenol in the presence of PTS, one-half of KP sphere-EtBS was made insoluble in benzene. The average molecular weight of the soluble fraction obtained by this treatment was 840, which was nearly equal to that before treatment. The structural features of the disk-like components in the spheres are summarized as follows. (l), The size of aromatic units is distributed over a wider range than the QI from original pitch. The smaller molecules (MW 400) as well as the larger ones (MW 3000) are the main components. (2), The average molecular weight of the spheres is about one-half that of the QI. (3), The major aliphatic hydrogens are located in side chains and the minor ones in methylene bridges. ( 4), The differences in molecules are aggregated in a nematic regularity. The difference in properties of these two auinoline insolubles. as far as carbonization and graphitization are concerned, are attributable to their structural differences.