Protocol describes an RNA Polymerase III (Pol III) transcription assay using an extract or proteins of choice. Pol III is the polymerase responsible for transcribing 5S RNA, tRNAs, and other small RNAs. α-Amanitin inhibits Pol II transcription in the assay. The newly-transcribed, radiolabeled RNA is visualized by autoradiography following Urea Polyacrylamide gel electrophoresis.