Abstract: A tool for implanting radioactive seeds for therapeutic purposes into living tissue such as a prostate gland includes an elongate hollow needle, an elongate hollow sleeve, and an elongate push rod. A plurality of axially aligned seeds and spacers are loaded into the sleeve, the sleeve is slideably inserted into the hollow needle, the needle is introduced into the tissue at a preselected site, and the push rod is used in a procedure that implants one or more seeds and spacers into the tissue. The sleeve is transparent or translucent so that the number of seeds and spacers remaining within the sleeve at any time is visually ascertainable.