The literature is confusing as to the need for anterior column fusion in the surgical treatment of patients with high-grade dysplastic spondylolisthesis. The current authors present an analysis of consecutive pediatric patients treated surgically for high-grade spondylolisthesis with and without anterior column structural support with emphasis on fusion rates, segmental kyphosis correction, and functional outcomes. Thirty-seven surgical procedures were done in 31 patients for Meyerding Grade 3 or Grade 4 isthmic dysplastic spondylolisthesis. Patients were separated into two groups based on whether they had structural anterior column support (tricortical autogenous iliac crest) in addition to posterior fusion surgery. Group 1 consisted of 18 patients treated only with posterior surgery without anterior structural support (11 patients were treated with L4-sacrum posterior in situ fusion and seven patients were treated with posterior instrumented reduction with decompression and posterior fusion), and Group 2 consisted of 19 patients who had a reduction and circumferential fusion including anterior structural support. All patients had new radiographs taken at the time of followup (average, 3.1 years, range, 2 years-10 years 1 month) and completed a functional outcome questionnaire. The incidence of pseudarthrosis was 39% (seven of 18 patients) in Group 1 and 0% (0 of 19) in Group 2. All seven patients who had pseudarthrosis achieved solid fusion with a second procedure involving circumferential fusion with anterior column structural grafting. Outcomes regarding pain after treatment, function, and satisfaction were high in those patients who achieved solid fusion regardless of surgical procedure.