Objectives: To determine if the OOPS index is predictive of long-term hearing results after ossiculoplasty. Study Design: Case series with retrospective chart review. Setting: Tertiary care otology practice. Patients: Adult and pediatric patients (3-88 years of age). Interventions: Ossiculoplasty with cartilage tympanoplasty, with or without mastoidectomy. Outcome Measures: Primary outcome measures included short-term hearing results (pure-tone average air-bone gap [PTA-ABG] measured between 60 days and 1 year after surgery), long-term hearing results (PTA-ABG measured >= 5 years after surgery), and the rate of successful ABG closure to <= 20 dB. Secondary measures included the need for revision surgery, delayed tympanic membrane graft failure, worsening conductive hearing loss (after an initially satisfactory hearing result), and recurrence of cholesteatoma. Results: There was no significant difference between adults and children for short-term hearing results (average post-op PTA-ABG was 18.9 dB vs. 19.8 dB, respectively; p = 0.544), long-term hearing results (average final PTA-ABG was 19.3 dB vs. 19.4 dB, respectively; p = 0.922), or rate of ABG closure to less than 20 dB (63.1% vs. 58.0%, p = 0.282). Spearman's rankorder correlation (p) identified a strong positive correlation between OOPS index score and average post-operative PTAABG (p = 0.983; p< 0.001; 2-tailed), as well as average longterm PTA-ABG (p = 0.950, p< 0.001; 2-tailed). Conclusions: The OOPS index makes it possible to accurately prognosticate hearing outcomes in adult and pediatric patients undergoing ossiculoplasty in both the short term and the long term.