Although ultrasonography is the most valuable and accurate diagnostic method for gallbla-dder empyema there is controversy regarding the layering phenomenon in gallbladder empy-ema. The purpose of this experimental study was to investigate whether layering occurs in gallbladder empyema or not. Six phantom specimens(the bile and the pus specimens and four mixed ones of bile and pus in a different composition ration) were examined to assess layering of internal echoes. 1. Layering can occur in the gallbladder empyema. 2. the higher the concentration of pus in specimen is the less probable the layering is to happen. 3. The longer the specimen is kept immobile the more probable the layering is to happen.