OBJECTIVE Metallic coils have been used for vascular embolization for many years but controlled-release coils have only recently become commercially available. Most of these devices are microcoils that were manufactured primarily for the packing of intracerebral aneurysms; therefore, they lack radial force and are not ideal agents for the occlusion of high-flow lesions such as pulmonary arteriovenous malformations (PAVMs). The objective of this study was to review our experience with a new detachable coil based on the conventional Gianturco-Wallace coil. METHODS The new detachable coil was initially used for the treatment of varicocele in 20 patients. Subsequently, the coil was used in 48 patients during 90 procedures for the treatment of PAVMs. RESULTS A total of 548 coils were used. Complete occlusion of the testicular vein was achieved in all patients with varicocele. Successful occlusion of the PAVM being treated was achieved in all patients, and no instances of recanalization were documented in any of the patients who returned for follow-up angiography. Forty-one coils had to be removed completely from the catheter before detachment because of inappropriate size or position. Eight coils failed to detach easily, and six of these had to be removed. Most of these device failures were associated with kinking of the screw thread mechanism between the coil and the delivery wire. CONCLUSIONS The Jackson detachable coil allows safer, more accurate, and more distal embolization of PAVMs than is possible with nondetachable coils. Complications associated with its use have been few.