Molecular-genetic analyses have revealed that the Archaea (archaebacteria) are phylogenetically distinct from both eukaryotes and eubacteria. Archaea lack nuclei and resemble eubacteria in morphology and genomic organization, but their molecular design shares many features with eukaryotes. Here, we review recent work that indicates that the archaeal transcriptional machinery is strikingly similar to the RNA polymerase I, II, and III systems of eukaryotic cell nuclei. These findings provide important insights into the evolution of the transcriptional apparatus.