The ultrasonic criteria for the diagnosis of gallbladder calculi are echo-dense structures which disturb the smooth contour of the posterior border of the gallbladder, sonic shadowing and echoes from within the gallbladder. Diagnostic confidence increases greatly in cases in which internal echoes, contour irregularities and sonic shadows occurred simultaneously. A case is presented in which all 3 criteria are fulfilled, but which represents an artifact, i.e., pseudostone. This was confirmed by varying the patient''s respiration and showing that the pseudostone represented echoes from a loop of bowel which produced a significant impression on the posterior wall of the gallbladder during deep inspiration. The absence of cholelithiasis was confirmed by oral cholecystography.