Minimally invasive and interbody and instrumented fusion techniques are increasingly being used for the treatment of adult degenerative disc disease, stenosis, and deformity of the lumbar spine. Advocates of minimal access spinal approaches list certain advantages over open procedures, including decreased postoperative pain and narcotic requirements, shorter hospital stays, less blood loss, and smaller incisions. The minimally invasive anterolateral approach allows access to the lumbar spine through the retroperitoneal space. We report on the short-term clinical and radiographic outcomes in four patients with mid to high lumbar coronal deformities treated at our institution with the anterolateral transpsoas minimally invasive approach. The primary presentation of these patients was back and leg pain. All patients showed improvement in their preoperative symptoms and solid arthrodesis at 6 months. Independent nonbiased patient pain analysis was also performed. Mean follow-up was 10 months (standard deviation, 1.4 mo), and mean hospital stay was 3.5 days (standard deviation, 1.9 d). One patient had additional posterior segmental instrumentation placed. Mean Cobb angles in the coronal plane were 28.5 degrees preoperatively and 18.3 degrees postoperatively (P < 0.05). We also present a historical perspective on retroperitoneal spine surgery, a regional anatomic description of the lumbosacral plexus and surrounding structures, and a description of the surgical technique as related to treatment of lumbar deformity.