In earlier papers we examined the stability of a resonant rotation rate for Venus. In the resonant rotation state the planet presents the same face to the earth at each inferior conjunction. The present investigation is concerned with the capture probability at this resonance. It is shown that trapping at the resonance can be understood if Venus possesses a fluid core similar to the earth's. Maximum capture probability occurs if the core responds to changes in angular velocity of the mantle with a time lag of about 3 X 10 yr. If Venus is in the resonant rotation state, then mapping of its gravitational field will determine the direction of its primordial rotation and may also permit an estimate of its magnitude.