This paper will present ongoing research in high frequency acoustic microscopy at the Penn State Ultrasonics Laboratory. The Penn State focus has been in the identification and development of new applications as well as the establishment of standards for acoustic microscopy. Recent work on the use of high frequency (400-600 MHz) acoustic microscopy for the qualitative and quantitative nondestructive characterization of materials (e. g. semiconductor thin films, protective and thermal barrier coatings, IC device packaging, etc. ) will be presented.