A surface acoustic wave (SAW) sensor is used to study the relative humidity response of polyimide films where interfacial and surface properties are varied. The relationship between these responses and the relative adhesion strength of these films is of particular interest since it could have application as a nondestructive, quantitative measure of adhesion strength. The results show clear differences in the SAW humidity response for cured and uncured films. There are also significant differences in the SAW humidity response for films applied with and without adhesion promoter. In addition the humidity response has proven to be particularly sensitive to the surface treatment of the polyimide film. These results suggest applications of the SAW sensor as a cure indicator, an in-situ sensor for the monitoring of film surface properties in process control applications and as an adhesion sensor.