  We determine the torque exerted in a steady state by an external potential on
a three-dimensional gaseous disk at a non-coorbital corotation resonance. Our
model accounts for the feedback of the torque on the surface density and
vorticity in the corotation region, and assumes that the disk has a barotropic
equation of state and a nonzero effective viscosity. The ratio of the torque to
the value given by the formula of Goldreich & Tremaine depends essentially on a
single dimensionless parameter, which quantifies the extent to which the
resonance is saturated. We discuss the implications for the eccentricity
evolution of young planets.
