Six patients with a prolonged history of severe muscular asthenopia caused by persistent convergence insufficiency underwent resection of both medial rectus muscles. A temporary consecutive esotrapia occurred in each instance and was controlled with prisms. Five weeks after surgery the consecutive esotropia had disappeared in all but one patient who still required prismatic correction for distance fixation. All patients experienced relief from their symptoms. Whereas orthoptic training is useful in most cases of convergence insufficiency a resection of both medial rectus muscles should be considered in persistent cases especially with an associated weakness of accommodation.