PROJECT SUMMARY Pathology using immunohistochemistry (IHC) remains a critical tool in modern clinical medicine. However, the capabilities of routine IHC methods have not kept pace with advances in biomedicine, which require evaluating networks of, e.g., tens of large molecules (typically protein targets) in a tissue context by multiplexing. To overcome this limit, highly multiplexed IHC imaging systems based on mass spectrometry and repeated Immunofluorescence (IF) imaging have been developed. These systems claim theoretical multiplexing of up to 100 targets. However, they are too slow, expensive, and complex, for routine use, and are currently used in a small number of research laboratories. We are working to radically change the capabilities of IF imaging to allow routine detection of tens of molecular targets rapidly and at moderate cost. Our approach builds on our previous work on high-speed hyperspectral imaging coupled with amplified molecular target labeling methods. We will advance our technology and demonstrate its capabilities with a specific research application involving imaging of brain sections from a mouse model of a neuropathology relevant for Alzheimer’s disease (AD). We will make improvements to achieve simpler and faster operation of our technology. We will then image up to 12 targets and demonstrate the ability to extend our approach to tens of targets on a single tissue slide. We expect our instrumentation and protocols will be sufficiently simple, low cost, and rapid to allow routine use in most pathology and research laboratories. !