The heterofunctional condensation reaction of 1,4-bis(phenyldichlorosilyl)benzene with dihydroxydiphenylsilane at a 1:4 ratio of initial compounds in the presence of pyridine was investigated and tetrakis(hydroxydiphenylsiloxy)-1,4-bis(phonylsilyl)benzene was obtained. The heterofunctional condensation of the tetrakis(hydroxydiphenylsiloxy)-1,4-bis(phenylsilyl)benzene with organotrichlorosilanes at a 1:2 ratio of initial compounds in the presence of pyridine produced dichloro-containing arylenecyclosiloxanes. The dichloro-containing arylenecyclosiloxanes were obtained in one stage by successive heterofunctional condensation of 1,4-bis(dichlorophenylsilyl)benzene with dihydroxydiphenylsilane and organotrichlorosilanes in a 1:4:2 ratio in the presence of pyridine. It was established that the yields of dichloro-containing products were lower. Hydrolysis of dichloroarylenecyclosiloxanes in a neutral condition produced corresponding dihydroxy compounds. Heterofunctional polycondensation of dicloro(dihydroxy)arylenecyclosiloxanes with alpha,omega -dihydroxy(bisdimethylamino)dimethylsiloxanes was used to obtain arylenecyclosiloxane-dimethylsiloxane copolymers. Thermogravimetric, thermomechanical, and roentgenographic investigations of the synthesized copolymers were carried out.