  A method of calculation of the scattering amplitude for fermions and scalar
bosons with exchanging of a scalar particle in ladder approximation is
suggested. The Bethe-Salpeter ladder integral equations system for the
imaginary part of the amplitude is costructed and solution in the Regge
asymptotical form is found. The corrections to the amplitude due to the exit
from mass shell are calculated and the real part of the amplitude is found.
