A brachytherapy needle for delivering radioactive seeds into the body of a patient comprises a tube into which the radioactive seeds and intervening spacers are loaded. The tube is telescopically disposed within a cutting cannula and is substantially longer than the cannula such that the cannula can be withdrawn over the tube, leaving the forward end of the tube exposed within the tissues of the patient. When the cannula is retracted, the seeds within the tube can be visualized using conventional medical imaging technology. The tube of the disclosed embodiment includes a deformable constriction which normally retains the seeds within the lumen of the needle but which deforms to permit the seeds to pass when subjected to a predetermined force. The tube of the disclosed needle has a low-friction exterior surface to prevent tissue from being displaced as the device is withdrawn. In yet another aspect the cannula and telescoping hollow tube are dimensioned such that when the cannula is withdrawn with respect to the tube, the blunt forward edge of the tube extends beyond the cutting edge of the hollow cannula to prevent accidental needle sticks.