The stability of albumin-bilirubin complex was investigated depending on pH of solution. It was shown that the stability of complex increases in presence of Mn (II) ions. It was also investigated the paramagnetic composition of gallstones by the Electron Spin Resonance (ESR) method. It was found that all investigated gallstones contain a free bilirubin radical-the stable product of its radical oxidation. Accordingly the paramagnetic composition gallstones could be divided on three main types: cholesterol, brown pigment and black pigment stones. ESR spectra of cholesterol stones is singlet with g=2.003 and Delta H=1.0 mT. At the same time the brown gallstones, besides aforementioned signal contain the ESR spectrum which is characteristic for Mn(II) ion complexes with inorganic compounds and, finally, in the black pigment stones it was found out Fe(III) and Cu(II) complexes with organic compounds and a singlet of bilirubin free radical. It is supposed that crystallization centers of gallstones could be the polymer network of bilirubin radical polymerization in complex with different metal ions.