||Study Design. Multicenter, prospective, consecutive series.Objective. Evaluate responsiveness of the SRS-Schwab adult spinal deformity (ASD) classification to changes in health-related quality of life (HRQOL) following treatment for ASD.Summary of Background Data. Ideally, a classification system should describe and be responsive to changes in a disease state. We hypothesized that the SRS-Schwab classification is responsive to changes in HRQOL measures following treatment for ASD.Methods. Multicenter, prospective, consecutive series from the International Spine Study Group (ISSG). Inclusion criteria: ASD, age>18, operative or non-operative treatment, baseline and one-year x-rays and HRQOL measures (Oswestry Disability Index [ODI], SRS-22, SF-36). The SRS-Schwab classification includes a curve descriptor and three sagittal spinopelvic modifiers (sagittal vertical axis [SVA], pelvic tilt [PT], pelvic incidence/lumbar lordosis mismatch [PI-LL]). Changes in modifiers at one year were assessed for impact on HRQOL from pre-treatment values based on minimal clinically important differences (MCID).Results. 341 patients met criteria (mean age = 54; 85% women; 177 operative and 164 non-operative). Change in PT modifier at one year follow-up was associated with changes in ODI and SRS-22 (total and appearance scores) (p≤0.034). Change in SVA modifier at one year was associated with changes in ODI, SF-36 PCS and SRS-22 (total, activity and appearance scores) (p≤0.037). Change in PI-LL modifier at one year was associated with changes in SF-36 PCS and SRS-22 (total, activity and appearance scores) (p≤0.03). Patients with improvement of PT, SVA, or PI-LL modifiers were significantly more likely to achieve MCID for ODI, SF-36 PCS (SVA and PI-LL only), SRS activity, and SRS pain (PI-LL only).Conclusions. The SRS-Schwab classification provides a validated system to evaluate ASD, and the classification components correlate with HRQOL measures. The current study demonstrates that the classification modifiers are responsive to changes in disease state and reflect significant changes in patient-reported outcomes.