The literature documents progression of spondylolisthesis, most commonly during the adolescent growth spurt. Twenty-eight patients with Grades I and II spondylolisthesis were treated with antilordotic braces. Presenting signs and symptoms included back pain (61%), tight hamstrings (53%), increased lordosis (25%), and mild scoliosis (21%). Three patients presented with spondylolysis and progressed to a slip prior to initiation of brace treatment. Mean duration of brace treatment was 25 months. In the brace, lateral roentgenograms demonstrated a significant reduction of lumbar lordosis and sacral inclination. At the conclusion of brace treatment all patients were pain-free and none had demonstrated a significant increase in slip percent.