Abstract: We describe a method for opening the blood-brain barrier (BBB) using ultrasound and preformed microbubbles. With this method, diagnostic or therapeutic agents may be administered to the brain. This method can open a focal region of the BBB and administer agents in a targeted fashion or the method can open large regions (or the entirety) of the brain for more global administration of agents. In one embodiment, the method can be used to administer contrast agents (e.g., agents that increase or decrease the magnetic resonance imaging signal) to the brain and thereby improve the quality or information content of imaging data. In another embodiment, a standard clinical diagnostic ultrasound scanner can be used to open specific regions of the BBB and administer diagnostic or therapeutic agents. Importantly, this invention can open the BBB in a non-destructive/non-invasive fashion, allowing the subject to be awake and suffer no detectable side effects.