Twelve thousand three hundred eighty-four (12,384) patients undergoing hip or knee arthroplasty were randomized to receive either aspirin (100 mg daily) (n=7,238) or enoxaparin (40 mg daily) (n=5,146) for 35 days after hip arthroplasty and 14 days after knee arthroplasty. The primary outcome was symptomatic venous thromboembolism (VTE) within 90 days. Secondary outcomes included joint-related reoperation, major bleeding, joint-related readmission, and all-cause mortality within 90 days, as well as joint-related reoperation within 6 months. Overall, symptomatic VTE occurred more frequently in the aspirin group compared to the enoxaparin group, favoring enoxaparin. Additionally, joint-related reoperation rates were slightly lower in the enoxaparin group. No significant differences were observed for major bleeding, readmission, or mortality. These findings suggest that enoxaparin is superior to aspirin in preventing symptomatic VTE following hip or knee arthroplasty.