  We consider the theory of four-fermion interactions with N-component fermions
in de Sitter space. It is found that the effective potential for a composite
operator in the theory is calculable in the leading order of the 1/N expansion.
The resulting effective potential is analyzed by varying both the four-fermion
coupling constant and the curvature of the space-time. The critical curvature
at which the dynamically generated fermion mass disappears is found to exist
and is calculated analytically. The dynamical fermion mass is expressed as a
function of the space-time curvature.
