Fifty patients with 8 prism diopters or less of esotropia after the last surgery were studied. Forty-nine percent of those straightened before 12 months of age and 41% of those straightened between 13-24 months developed the M.S. Only one of 22 patients straightened after the age of two developed the M.S. Although D.V.D and overaction of the inferior oblique muscles were associated findings, neither precluded the development of the M.S. Those patients without M.S. had a higher incidence of subsequent exotropia and manifest D.V.D.