Two cobalamin biosynthetic genes from the archaeon Pyrococcus sp. KOD1 were cloned and sequenced. A 4.4 kb HindIII fragment from KOD1 comprised of two genes designated cobQ (1,422 bp) and cob V (696 bp) encode cobyric acid synthase (MW, 52,643 Da) and cobalamin (5’-phosphate) synthase (MW, 25,285 Da), respectively. The cob locus was identified on a chromosomal map of KOD1. The presence of cob genes in KOD1 and other methanogens suggests that the cobalamin biosynthesis pathway found in bacteria is also present in archaea.