DNA replication initiation, which starts at specific chromosomal site (known as 
replication origins), is the key regulatory stage of chromosome replication. 
Archaea, the third domain of life, use a single or multiple origin(s) to 
initiate replication of their circular chromosomes. The basic structure of 
replication origins is conserved among archaea, typically including an AT-rich 
unwinding region flanked by several conserved repeats (origin recognition box, 
ORB) that are located adjacent to a replication initiator gene. Both the ORB 
sequence and the adjacent initiator gene are considerably diverse among 
different replication origins, while in silico and genetic analyses have 
indicated the specificity between the initiator genes and their cognate origins. 
These replicator-initiator pairings are reminiscent of the oriC-dnaA system in 
bacteria, and a model for the negative regulation of origin activity by a 
downstream cluster of ORB elements has been recently proposed in haloarchaea. 
Moreover, comparative genomic analyses have revealed that the mosaics of 
replicator-initiator pairings in archaeal chromosomes originated from the 
integration of extrachromosomal elements. This review summarizes the research 
progress in understanding of archaeal replication origins with particular focus 
on the utilization, control and evolution of multiple replication origins in 
haloarchaea.