The stability of the linear orthorhombic polymer Of C-60 as a function of pressure has been studied by Raman scattering and X-ray measurements. The in situ Raman study shows an irreversible transition to a new phase occurring at pressures as low as similar to 0.3 GPa. The specimens treated at pressure up to 3 GPa without laser irradiation do not show any structural changes after pressure release. The Raman spectrum of the new phase differs from, those of the known 2D polymerized phases of C-60. These data indicate that the simultaneous application of pressure and laser irradiation results in pressure photoinduced polymerization of the pristine polymeric chains of C-60 thus transforming it to a new polymeric phase Of C-60.