A variety of non-thermal effects of biomedical ultrasound has been observed both in intact plant roots and in cultured mammalian cells in suspension. However, several qualitative differences in response between these two systems make extrapolation to mammalian in vivo systems difficult. The proposed research will examine the effects of biomedical ultrasound, alone and in combination with mild hyperthermia, on Chinese hamster and Indian muntjac cells in monolayer culture. Monolayer cells, because they are fixed in place like cells in structured tissues, yet without the cell walls or air spaces of plant roots, may approximate mammalian cells in vivo more closely than either plant roots or suspension cells. Specific endpoints to be studied include: (1) cell lethality as a function of intensity for continuous wave exposure, (2) cell lethality as a function of pulse length for pulsed exposure, and (3) possible induction of chromosomal anomalies. In each of these three areas qualitative differences exist between plant roots and suspension cells; examination of monolayer cells is expected to clarify the mechanisms responsible for these differences. By better elucidating the mechanisms of ultrasound action the proposed research should aid in evaluating the potential risks and benefits of biomedical ultrasound as a diagnostic and therapeutic agent.