Recent progress in cell cycle analysis of archaea has included the identification of putative chromosome replication origins, novel DNA polymerases and an unusual mode of cell cycle organization featuring multiple copies of the chromosome and asymmetric cell divisions. Genome sequence data indicate that in crenarchaea, the 'ubiquitous' FtsZ/MinD-based prokaryotic cell division apparatus is absent and division therefore must occur by unique, as-yet-unidentified mechanisms. The evolutionary and functional relationships between the archaeal Cdc6 protein and bacterial and eukaryal replication initiation factors are discussed.