The role of cavitation in bulk ultrasound ablation has been evaluated in a series of in vitro experiments. Fresh bovine liver tissue was ablated with a 3.1 MHz ultrasound image-ablate probe at 31 W/cm 2 for 20 minutes under normal and elevated ambient pressures. A 1 MHz passive cavitation detector recorded acoustic emission signals which were quantified by computation of average subharmonic, broadband, and low-frequency emission levels. After ablation, tissue was sliced and stained with 2% TTC to evaluate thermal damage. Emission levels were quantified and correlated with tissue ablation histology. The results indicate that bubble activity significantly affects heat deposition in ultrasound bulk ablation, in a manner different from high-intensity focused ultrasound (HIFU) ablation.