The pathway and mechanism of convergence movement of eyes are not exactly confirmed at now. But, according to the recent neurophysiologic studies, the convergence cells was found in an area of the mesencephalic reticular formation just dorsal and lateral to the oculomotor nucleus and rostral to the superior colliculus. I experienced four patients, who complained diplopia due to unilateral convergence palsy. These cases of unilateral convergence palsy suggests that the Rt. Convergence cells and the Lt. Convergence cells in the mesencephalic reticular formation has independent pathway to ipsialteral medial rectus motoneuron nucleus.