Under an SBIR Phase II grant, a laser diagnostic instrument will be further developed for the diagnosis of bubbles due to cavitation in flow systems. The principle of the diagnostic method is phase doppler interferometry. Identification of particles as either solid or bubble, and determination of orientation and shape of bubbles, will be attempted with the new instrumentation first in preliminary validation experiments and then in actual cavitating conditions. Cavitating flow diagnosis will permit better understanding of, and development of better predictive models for, flows applicable in chemical engineering, nuclear engineering, and biological systems.