An inorganic enhancement agent ( EA) for high-intensity focused ultrasound (HIFU) imaging based on mesoporous silica nanocapsules is presented. The pronounced coagulative necrosis effects demonstrate, both in vitro and in vivo, that the EA can be developed as a highly promising theranostic agent for effective HIFU imaging and therapy owing to its high stability, efficient perfluorohexane loading and release, enhanced tumor ablation capability, and easy uptake by target tissues.