Microbubble agents have been shown to increase therapeutic effect of HIFU (High intensity focused ultrasound). Here, the effects of treatment parameters on lesion volume and temperature are investigated. Ex vivo tissue was treated with a 2 MHz HIFU beam in absence and presence of the Artenga microbubbles at varying HIFU focal intensities (600-2300 W/cm2), microbubble concentrations, and exposure durations (3-10 s). The temperature was measured at 1 mm from focus using a K-type thermocouple. Thermal lesion volume was measured based on an ellipsoid model. Microbubbles increased the lesion volume and peak temperature achieved with HIFU. At 2316 W/cm2 intensity, the lesion volume increased by 2-folds, and the peak temperature increased by 16 ⁰C with microbubbles. This effect depended on microbubble concentration, ultrasound intensity and exposure duration. Lower intensities and shorter time durations were required at higher microbubble concentrations to ablate the tissue. It was concluded that the efficacy of the HIFU therapy in combination with microbubbles can be controlled through ultrasound/ microbubble exposure parameters.