Two series of patients who had superior oblique tenotomies either alone or in combination with horizontal muscle surgery were evaluated, and the results and complications were analyzed. The effect of bilateral superior oblique tenotomies in downgaze correlated well with the previously reported series. In these two series, the effects in primary and upgaze also were evaluated. An average effect of 12 prism diopters eso-shift was found to occur in primary position, while no eso- or exo-shift was found in upgaze. Operative indications and contradictions, when followed carefully, make predictable the effectiveness of the operation in collapsing an A pattern. The reported unequal effects on superior oblique action were not observed in any of the patients studied. In no instance in these series was there a worsening of preexisting hypertropia or development of a new one. Transient sheathlike Brown's syndrome occurred postoperatively in some patients in the early series, but this problem was reduced by the instillation of steroid suspensions. V patterns developed postoperatively in 20 percent of the cases in the first series and in 9 percent in the second series. There was approximately a one-in-three chance that the inferior oblique muscle would become slightly to moderately overactive postoperatively. The incidence of this complication will be reduced significantly or eliminated by careful case selection to choose only those patients who have slightly underactive inferior oblique muscles preoperatively.