RNA polymerase C represents the major form of RNA polymerase activity solubilized from the Xenopus laevis ovaries. After partial purification, it can be resolved in two forms by DEAE-Sephadex chromatography. Both are able to transcribe efficiently an intact DNA template, either high molecular weight Xenopus DNA or intact adenovirus DNA. Amplified ribosomal DNA is transcribed asymmetrically by RNA polymerase C : 90% of the RNA synthesized in vitro hybridizes to the H-strand. In contrast, RNA polymerase A has little activity on an intact DNA template and transcribes both strands of ribosomal DNA with equal efficiency.