The photochemical degradation of the homogeneous oxygen-saturated buffered aqueous solutions of sodium heparin salt initiated by the irradiation with medium pressure mercury lamp was compared with the heterogeneous photocatalytic heparin degradation sensitized by titanium dioxide. The obtained results confirmed that UV irradiation of heparin homogeneous aqueous solutions caused negligible changes in the polysaccharidic structure only. The irradiation of heparin in oxygen-saturated physiological saline photosensitized by the TiO2 caused significant changes in the heparin macromolecule. The study of photocatalytic heparin degradation in buffered oxygen-saturated TiO2 suspensions (pH=5-9) ascertained a significant influence of pH on the degradation of heparin. The polymeric chain is predominantly cleaved in the acidic and neutral medium.