Implanted venous access devices (IVAD) are routinely used in oncologic patients. Thrombotic complication is a source of morbidity. During one year 246 patients with different solid neoplastic diseases received IVAD for chemotherapy administration. Two hundred forty-nine IVAD were placed percutaneously or by surgical cutdown. IVAD were flushed immediately after implantation with 3-5 mL of heparinized saline (100 U/mL). No monthly flush was required. A prospective evaluation of thrombotic complications was realised. in event of catheter dysfunction and/or clinical symptoms of phlebitis, a catheter opacification and/or a Doppler ultrasonography were performed. Twenty-three catheter dysfunctions were noted, corresponding to 13 catheter occlusions. Twelve patients presented clinical symptoms of phlebitis. Eleven venous thrombosis were diagnosed in this group; 10 by echo-Doppler and one by scanography. A unvaried statistic analysis using Fisher's test was performed to detect risk factors. Two factors were identified: the position of catheter tip above T4 (p < 0.001) and mediastinal or cervical lymph nodes larger than 6 cm (p < 0.001). The first increased the risk of catheter occlusion and the second increased the risk of phlebitis.