  We estimated the magnetic field strength of compact stars in X-ray binaries
Sco X-1 and Cyg X-1, via various methods of determination of magnetic fields.
For Sco X-1 we used three independent methods. One of them is based on the
correct account of the Faraday rotation of polarization plane in the process of
electron scattering of X-rays from accreting neutron stars. Numerical
calculations are made with use of first X-rays polarimetric data presented by
Long et al. (1979). Other original method of determing the magnetic field
developed by Titarchuk at al. (2001) is based on observed quasi-periodic
oscillations (QPO) frequencies in X-ray binaries that can be considered as
magnetoacoustic oscillations of boundary layer near a neutron star. The optical
polarimetric data obtained in 70-th have been also used for estimation of
magnetic field of the neutron star in Sco X-1 and of nearest environment around
the black hole in Cyg X-1.
