Abstract: In the present paper the nonlinear systems with energy-dependent nonconserva-tive forces are considered. The exact probability density functions of the stationary response of four classes of such systems to white noise external and/or parametric excitations are constructed. The conditions under which the steady-state solution exists are discussed. It is pointed out that all the steady-state solutions available up to now are special cases of the present solutions. Several examples are also given to illustrat...