Seventy-two consecutive patients with totally implanted catheters for administration of chemotherapy for solid tumours or lymphomas were studied prospectively to assess the prevalence of venous thrombosis. During the follow-up period of 343 (6-1,177) days, 11 cases of venous thrombosis (15.2%), of which 45% were partial and only 36% symptomatic were observed. Venous thrombosis was an early complication, 6/11 cases being observed within 1 month of implantation. No clinical or biological predisposing factor, apart from the presence of malignant disease, could be identified. Doppler ultrasonography is a good method of following-up these patients. This method should become an essential diagnostic tool in this field.