The Eaton group develops new electron paramagnetic resonance (EPR) methods and instrumentation to address significant biochemical and chemical problems. A major current emphasis is on EPR methods to improve sensitivity and solve biomedical problems. The conventional approach to detection of signals from unpaired electrons detected only a small fraction of the intensity on each slow pass through the spectrum. By scanning much faster and changing the detection hardware we have achieved dramatic improvements in signal-to-noise, which is key to observing weak signals in living systems. Hardware was developed to implement the rapid scan method and software was written to analyze the data. Advances in digital electronics are enabling much greater flexibility in the way experiments can be designed and modified. We are developing fully digital EPR spectrometers. In collaboration with research groups at the University of Chicago and University of Maryland we are developing methods for imaging local oxygen in vivo and methods for in vivo study of the physiology of tumors. Our team includes chemists, biochemists, physicists, and engineers. Our instrumentation includes state of the art Bruker BioSpin and locally-constructed spectrometers. In our lab we currently have 8 EPR spectrometers operating at frequencies between 250 MHz and 34.5 GHz. Most of these spectrometers have major components that have been designed and built locally. Spectrometers at 250 MHz, 1 GHz and 9.5 GHz have capabilities for rapid scans and imaging. In collaboration with other groups we study protein conformations. We have characterized electron spin relaxation processes and can now base design of new spin probes on predictions for improvement of specific properties. Dissemination to the research community, in addition to over 300 research papers and reviews, includes a book on EPR imaging, a book on quantitative EPR, and major book chapters about electron spin relaxation and rapid scan EPR. Details about the EPR center can be found on its website.