It has been found that surface acoustic waves (SAW) exhibit a very large interaction with appropriately prepared thin magnetic films through the magnetoelastic effect. For a 600 Å 90Ni 10Fe thin film, the interaction can produce changes in attenuation of 30 dB/cm at 700 MHz by changing from 2 to 12 G a magnetic field applied parallel to the film plane and perpendicular to the SAW. Measurements of the frequency dependence of this large effect yield values for the Gilbert damping constant and the anisotropy field. This interaction has been studied in the series ofxNi (1 −x)Fe alloy films. Forx>80 wt %, the magnetoelastic constant η is negative. It is positive forx<80 wt%. An amorphous film with positive η has also been studied. Some device concepts which make use of this effect will be presented. [Work supported by the National Science Foundation under Grant No. ESC 8519695.]