Abstract. Intraoperative pulmonary embolism can occur not only during cemented total hip arthroplasty (THA) but also during cementless THA. In the present study, we demonstrated the usefulness of the ROBODOC femoral milling system in reducing intraoperative pulmonary embolism, as indicated by results of transesophageal echocardiography and hemodynamic monitoring. A prospective clinical trial was conducted with 58 patients (60 hips) who were randomly divided into 2 groups: group 1, 38 patients (40 hips) who underwent cementless THA with preparation of the femoral canal using ROBODOC; group 2, 20 patients (20 hips) who underwent conventional manual cementless THA surgery. During femoral preparation, severe embolic events were observed at a significantly lower frequency in group 1 (0%) than in group 2 (30%) (p<0.0001). During stem insertion, incidence of severe embolic events was significantly lower in group 1 (0%) than in group 2 (20%) (p<0.0001). Moreover, during hip relocation, incidence of severe embolic events was significantly lower in group 1 (8%) than in group 2 (45%) (p<0.0001). The ROBODOC system decreased the incidence of severe embolic events during femoral preparation, resulting in low incidence of severe events during stem insertion and hip relocation. The present results suggest that the ROBODOC femoral milling system may reduce the risk of pulmonary embolism during cementless THA.