Non-contrast and contrast applications of 10 - 80 MHz micro-ultrasound will be described. Imaging of cardiovascular, prostate, hepatocellular carcinoma, and melanoma models will be used to demonstrate vessel detectability down to 50 microns using the native contrast of blood and down to the capillary microcirculation using microbubble contrast agents. By labeling the microbubbles with appropriate ligands it is possible to perform molecular imaging of endothelial cell surface markers. Examples of molecular imaging of VEGFR-2 expression in a variety of tumor models will be demonstrated with the new array imager. Applications in developmental biology, musculoskeletal disease, inflammation, atherosclerosis and a wide variety of other mouse models of human disease will benefit from this technology. One of the limitations of the current contrast modes available for micro-ultrasound is their reliance on linear subtraction methods. This talk will focus on the implementation of a real-time nonlinear contrast mode on this array based system, and the challenges faced in high-frequency contrast imaging, namely nonlinear propagation in tissue. The array transducer, beamforming techniques, digital sampling and signal processing will be described, along with in vitro and in vivo results.