Electron Paramagnetic Resonance (EPR) is most often performed in microwave frequency bands, with X-band (~9.4 GHz) being the most common. With superconducting magnets, one can explore higher frequency EPR spectroscopy.   This has mostly been done at low rf power due to difficulties in obtaining high rf power levels as one approaches mm-wave frequencies.  There has been a good bit of low power continuous wave (CW) EPR at higher frequencies, but the lack of high power and high bandwidth pulse amplifiers has limited pulse EPR instrumentation.  We have incorporated a UC-Davis designed vacuum tube amplifier (travelling wave tube design) into a new high power 263 GHz pulse EPR spectrometer.  I will show results on d-block and f-block high spin transition metal complexes, including manganese and gadolinium sequestering proteins. The utility of this instrument in a variety of studies of paramagnetic systems will be discussed, including applications in quantum information science, molecular magnets, EPR spectroelectrochemistry, and dynamic nuclear polarization.