1. Small sections cut from commercial crates used to transport live poultry to the processing plant were artificially contaminated with effluent taken from a commercial crate-cleaning system. 2. Laboratory trials, involving the immersion of these sections in an ultrasonic water bath (4 kW energy) showed that aerobic plate counts (APC) and counts of Enterobacteriaceae were progressively reduced as the immersion time was increased from 0 to 120 s and the water temperature raised from 35 to 58°C. 3. In subsequent trials at a processing plant, using commercially cleaned crates, there was relatively little effect of ultrasound (or pressure washing) on the biofilm present. However, ultrasonic treatment in combination with an immersion temperature of 60°C reduced counts of Enterobacteriaceae to below the detection limit (log 10 2·3 cfu) within 1 to 3 min, while APC were reduced by >2 log10 units after 3 min. 4. It was concluded that ultrasonic treatment has a possible role in the crate-cleaning process, when used in conjunction with higher immersion temperatures. In this way, it could contribute significantly to hygiene control.