Thirty-one severe, symptomatic valgus deformities of the hindfoot in twenty children who had flatfoot (twenty-five feet) or skewfoot (six feet) were corrected with a modification of the calcaneal lengthening osteotomy described by Evans. Despite prolonged non-operative treatment, all patients had pain, a callus, ulceration, or a combination of these signs and symptoms under the head of the plantar flexed talus; they could not tolerate a brace, and shoe wear was excessive. Twenty-six of the deformities were secondary to an underlying neuromuscular disorder. The calcaneal lengthening was combined with an opening-wedge osteotomy of the medial cuneiform to correct the deformities of both the hindfoot and the forefoot in the patients who had a skewfoot. Other concurrent osseous and soft-tissue procedures were frequently performed in the flatfeet and skewfeet to correct adjacent deformities or to balance the muscle forces. Allograft bone was used in twenty-four feet and autogenous bone, in seven. The patients ranged in age from four years and seven months to sixteen years at the time of the operation. The duration of follow-up ranged from two years to three years and seven months after the operation. Satisfactory clinical and radiographic correction of all components of the deformity of the hindfoot was achieved in all but the two most severely deformed feet. These two feet had sufficient correction to eliminate the symptoms despite a small persistent callus under the head of the talus. The pain and callus were eliminated in all of the other feet, the patients were able to tolerate a brace, and shoe wear was improved. Subtalar motion was preserved in all feet except for the four that had had a limited joint arthrodesis performed previously or simultaneously for pre-existing degenerative osteoarthrosis. Calcaneal lengthening is effective for the correction of severe, intractably symptomatic valgus deformities of the hindfoot in children. My patients had resolution of the signs and symptoms associated with the deformity while avoiding the need for an arthrodesis and the many short and long-term complications associated with it.