A biopsy site marker comprises small bodies or pellets of gelatin which enclose substantially in their interior a radio (X-ray) opaque object. The gelatin pellets are deposited into the biopsy site, typically a cylindrical opening in the tissue created by the recent use of a vacuum assisted large core biopsy device, by an applicator device that includes an elongated cylindrical body that forms a flexible tube and a piston slidable in the tube. One end of the tube is placed into the biopsy site. Typically, several gelatin pellets, only some of which typically do, but all of which may contain the radio opaque object, are deposited sequentially into the site through the tube. The radio opaque objects contained in the gelatin bodies are of a non-biological configuration and readily identifiable as man-made object, so that in observation by typical mammography equipment they do not assume the shape of a line, whereby they are readily distinguishable from granules and lines of calcification.