In adults, symptomatic scoliosis is usually a de novo primary degenerative deformity that develops in the fifth or sixth decade or an unrecognized or untreated idiopathic deformity with superimposed degeneration. The evaluation and treatment of adult scoliosis must focus on addressing patient symptoms while limiting the consequences of the treatment. The presence of neurological deficits, the flexibility of the deformity, the coronal and sagittal balance, and status of spinal segments outside of the main deformity are all important considerations when planning surgery. The complication rate of deformity surgery in adults is potentially high; but excellent functional outcome and patient satisfaction can occur with thorough preoperative patient education and meticulous surgical technique.