The present study is concerned with the specific nature and the multiformity of microtropia, which is characterized by unilateral convergent small angle (under 10delta) strabismus with amblyopia and abnormal retinal correspondence. Three types of microtropia may be distinguished: Type I: Showing a positive cover test, amblyopia and abnormal retinal correspondence. Type II: Showing in addition to the above, heterophoria. Type III: Showing a negative cover test, a positive 4delta base-out prism test, amblyopia due to anisometropia, eccentric fixation and harmonious abnormal retinal correspondence, where the angle of anomaly is equal to the angle to eccentricity. For the prevention of microtropia all children aged under 4 and irrespective of the presence of any symptoms should undergo an eye examination. At a more advanced age the diagnosis of this clinical entity is of importance chiefly from a prognostic point of view, because it permits us to avoid futile efforts at correcting visual acuity by means of covering up to sound eye.