The sensorial structures located at the myotendinous junction of the extraocular muscles of patients suffering from congenital strabismus have been studied. Important alterations of these receptors have been observed, both at light and electron microscopy. The receptors appear smaller, with an inner capsule dividing the tendinous component into irregularly shaped compartments. At electron microscopy it is possible to identify: (1) receptors still possessing their architecture and nerve component but with modified nerve ending features and relationship with the Schwann cell covering; (2) receptors maintaining their general architecture but completely lacking the nerve component; (3) receptors where also the general architecture is completely disorganized. All these alterations seem to indicate that in strabismics the reception and transmission of proprioceptive information are abnormal and support the hypothesis that a disturbance of ocular proprioception can play an important role in the pathogenesis of congenital strabismus.