The high-pressure states of C-60 fullerene corresponding to the 1.5 GPa isobaric section of its p,T diagram in the 293-1073 K temperature range were investigated by X-ray diffraction and IR and Raman spectroscopies. It was shown that increasing the treatment temperature of C-60 at quasihydrostatic pressure changes the nature of the polymerization products. The IR and Raman spectra of the high-pressure materials obtained at 423 K are similar to the spectra of the dumb-bell-shaped C60 dimer synthesized in a solid-state mechanochemical reaction of C60 With potassium cyanide by Wang et al.(1) It can be concluded that this dumb-bell-shaped dimer is the main structural unit forming the low-pressure polymerization product. So, on further temperature increase, the dimer phase becomes unstable and transforms into the "low-pressure" orthorhombic polymerized phase of C60 which, in turn, transforms into the tetragonal polymerized phase at temperatures above similar to 723 K. Depolymerization of the polymerized phases at temperatures above similar to 900 K results in the formation of the monomeric fee phase of C60 fullerene, which agrees with the experimental data determined previously by Bashkin et al.(2).