A biopsy site marker having at least one small marker body or pellet of bioresorbable material such as gelatin, collagen, polylactic acid, polyglycolic acid which has a radiopaque object, preferably with a non-biological configuration. The at least one bioresorbable body or pellet with a radiopaque object is deposited into the biopsy site, by a delivery device that includes an elongated tubular body with a piston slidable within the tubular body. One end of the tube is placed into the biopsy site. At least one but preferably several marker bodies or pellets are deposited sequentially into the biopsy site through the tube. At least the bioresorbable materials of the detectable markers remain present in sufficient quantity to permit detection and location of the biopsy site at a first time point (e.g., 2 weeks) after introduction but clear from the biopsy site or otherwise do not interfere with imaging of tissues adjacent the biopsy site at a second time point (e.g., 5-7 months) after introduction.