When pitch material was heat-treated at 350-450°C, carbonaceous mesophase spherules formed in the pitch. Mesophase spherules separated from the pitch as quinoline insoluble matter. The separated spherules were so-called meso-carbon microbeads (MC). Chemical reactivities of the MC were investigated from nitration, amination, chlorination and Friedle-Crafts reaction.The following results are obtained.1) Nitration or chlorination of the MC occures easily, and aminated MC is yielded nearly quantitavely by reduction of the nitsated MC.2) Molecular weight of the MC based on a nitrogen atom in the nitrated MC is 100-170, this value shows that nitro group reacts not only with hydrocarbon existed the surface of the MC, but also with internal hydrocarbon.3) Optically anisotropic nature of the MC do not change with reactions of nitration, amination or chlorination, but the MC is transfered optically isotropic one by Friedle-Crafts reaction.4) From above mentioned results, it is recognized that molecules constructing the MC change easily these molecular structure with chemical reaction even if molecules are stacked in alignment in the MC.