Objective To examine the relationship between hospital procedure volume and surgical outcomes following elective primary total hip arthroplasty/total knee arthroplasty (THA/TKA). Methods Using the Pennsylvania Health Care Cost Containment Council database, we identified all patients who underwent elective primary THA/TKA in Pennsylvania. Hospitals were categorized according to the annual volume of THA/TKA procedures, as follows: â&25, 26-100, 101-200, and ;gt&200. The 30-day complication rate and 30-day and 1-year mortality rates were assessed by logistic regression models, adjusted for age, sex, race, insurance type, hospital region, 3M All Patient Refined Diagnosis Related Group risk of mortality score, hospital teaching status, and bed count. Results In the THA and TKA cohorts, the mean age of the patients was 69 years, and 42.8% and 35%, respectively, were men. Compared with patients whose surgeries were performed at very-high-volume hospitals (;gt&200 procedures/year), patients who underwent elective primary THA procedures at hospitals with a very low volume (a;circ25 procedures/year), a low volume (26-100 procedures/year), or a high volume (101-200 procedures/year) had higher multivariable-adjusted odds ratios (ORs) for venous thromboembolism (OR 2.0, 95% confidence interval [95% CI] 0.2-16.0), OR 3.4 [95% CI 1.4-8.0], and OR 1.1 [95% CI 0.3-3.7], respectively) and 1-year mortality (OR 2.1 [95% CI 1.2-3.6], OR 2.0 [95% CI 1.4-2.9], and OR 1.0 [95% CI 0.7-1.5], respectively). Among patients ages ≥65 years who underwent elective primary TKA at very-low-volume, low-volume, and high-volume hospitals, the ORs for 1-year mortality were significantly higher (OR 0.6 [95% CI 0.2-2.1], OR 1.6 [95% CI 1.0-2.4], and OR 0.9 [95% CI 0.6-1.3], respectively), compared with very-high-volume hospitals. Conclusion Performance of elective primary THA and TKA surgeries in low-volume hospitals was associated with a higher risk of venous thromboembolism and mortality. Confounding due to unmeasured variables is possible. Modifiable system-based factors/processes should be targeted to reduce the number of complications associated with THA/TKA procedures. Copyright © 2011 by the American College of Rheumatology.