We performed a prospective randomized controlled study to determine whether drainage increased the degree of anemia after primary cementless total hip arthroplasty. After implanting the components, we randomly divided 40 patients (40 hips) into a group who had drains (20 patients, 20 hips) and a group without drains (20 patients, 20 hips). There were no differences in the mean preoperative hemoglobin or hematocrit values, length of skin incision, operative time, intraoperative blood loss, or the donated and transfused volumes of autologous blood between the two groups. There were also no differences in decreased hemoglobin or hematocrit values 3 days postoperatively compared with preoperative values (hemoglobin, 0.7 g/dL versus 0.7 g/dL; hematocrit, 2.2% versus 2.4%). Drainage did not increase the degree of postoperative anemia after cementless total hip arthroplasty.