Abstract: A modular device for implanting radioactive seeds in an animal body through a needle implanted in the body. The device comprises an electronic control device controlling a pushing drive, a seed and spacer supply container, a multichannel holder for seed-spacer trains. A tube connects between the multichannel holder and the needle. The needle is retractable by retracting means coupled to the needle. Optionally the retracting means are controlled by the electronic control device. The device may also be embodied in a combination of a seed loading module in which trains of seeds are loaded in channels in a removable multichannel holder and a seed implanting module in which trains of seeds from a multichannel holder are pushed into needles implanted in the body. Parts that may be contaminated with blood are made removable for sterilization or disposal.