Using an institutional joint registry, we studied frequency, trends and predictors of mortality after elective total hip or knee arthroplasty (THA/TKA). Of the 12-727 and 12-484 patients who underwent THA and TKA, respectively, all-cause mortality rates at 7-, 30-, and 90-days were as follows: THA, 0.1%, 0.2%, and 0.5%; TKA 0.1%. 0.2%, and 0.4%, respectively. Statistically significant downward time trend in 90-day mortality was noted after TKA (P = .02) but not after THA (P = .41). In multivariable-adjusted analyses of patients undergoing THA, older age, higher comorbidity index, and prior cardiac disease were significantly associated with higher 90-day mortality. In patients undergoing TKA, older age, male gender, a Society of Anesthesiologist class of III-IV, and higher comorbidity index were associated with higher 90-day all-cause mortality. Optimization of disease management may reduce postoperative mortality after THA/TKA. © 2012.