We have recently obtained high resolution three dimensional crystals of Pol II at atomic resolution diffraction. We are now pursuing modified crystals, including a tight binding inhibitor and cocomplexes with DNA and DNA/RNA ternary complexes as simple routes to heavy atom derivatives. We have improved our crystals from an earlier limit of 30 w for unfrozen crystals to better than 3.5 w on our recent run using flash freezing and are attempting to improve the purity of the protein for lower mosaicity. Simultaneously, we are attempting to obtain the lowest resolution reflections for a direct phasing of the protein.