Fifteen patients had an oblique osteotomy of the tibia for the correction of a multiplanar deformity between January 1989 and March 1991; twelve were followed for an average of twenty-five months (range, twelve to forty-two months). Preoperatively, the average deformity in the coronal plane was 14 degrees (range, 30 degrees of valgus to 25 degrees of varus) and the average deformity in the sagittal plane was 13 degrees (range, 40 degrees of recurvatum to 23 degrees of procurvatum [angulation convex anteriorly]). The average leg-length discrepancy was 2.2 centimeters (range, one to six centimeters). No patient had a rotational deformity. After careful preoperative planning, all patients had an oblique osteotomy and placement of a lag screw and a neutralization plate. Somatosensory evoked potentials were monitored during any axial lengthening. A fibular osteotomy and lengthening of the Achilles tendon were performed as needed. Full weight-bearing on the extremity was prohibited until radiographic and clinical examination indicated that union had occurred, which was at an average of 4.5 months (range, three to six months). At the most recent follow-up examination, ten patients had an excellent result. The average correction in the coronal plane was to within 1 degree (range, 0 to 3 degrees) of normal and the average alignment in the sagittal plane was to within 2 degrees (range, 0 to 12 degrees) of normal. An average of 1.3 centimeters (range, 0.5 to 2.5 centimeters) of lengthening was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)