It was recently reported that certain antigens can be retrieved from paraffin sections of formalin-fixed tissues by ultrasonication using either an expensive and sophisticated ultrasonic cell disrupter probe (cytokeratins 13 and 16) or an inexpensive and generally available ultrasonic cleaning bath (bcl-1). We wished to investigate the routine use of the latter method and therefore tried to retrieve from various tissues 11 antigens that usually require heat-mediated retrieval in citrate buffer. We applied ultrasonic vibration for periods of 30 seconds to 1.5 minutes in a cleaning bath containing citrate buffer or water, with and without the addition of heat, or for 1 minute in hot citrate buffer after microwaving for 10 minutes in the same buffer. Although a slight effect of ultrasound was noted for a few antigens, in no case did the immunostaining reach the level achieved after standard microwave heating in citrate buffer. We conclude that, under the conditions we used, ultrasonic antigen retrieval cannot be used for immunocytochemistry in a routine histopathology laboratory.