A method of generating very strong focused negative pressure fields in water for cavitation studies from shock waves produced by an electromagnetic transducer is described. By using a reflecting concentrator with a phase-inverting central element, focal pressures of around−16 MPafrom a+5-MPasource have been measured. The combination of an electromagnetic transducer and a phase-inverting parabolic concentrator provides a reliable and reproducible source of cavitation bubbles for study. A qualitative study of the cavitation field produced by the device, using a laser schlieren technique, is presented.