Calf thymus (CT) RNA polymerase II bound to hamster papovavirus (HaPV) DNA was visualized by electron microscopy and compared to binding sites obtained after binding of Escherichia coli RNA polymerase to the HaPV genome. Thirteen binding sites were observed with CT polymerase II at map positions 0.04-0.07; 0.11; 0.18; 0.30; 0.37; 0.47; 0.57; 0.65; 0.78; 0.83; 0.90 and 0.94 using the unique BamHI cleavage site as zero point on the HaPV physical map. These binding sites correlate well with A + T rich sequences within the HaPV DNA as revealed by experiments using protein 32 coded for by phage T4. A comparison of binding of prokaryotic and eukaryotic RNA polymerase demonstrates a high degree of correspondence for most of the binding sites on the HaPV genome.