Strains of hyperthermophilic anaerobic hydrothermal vent archaea maintained in the culture collection assembled by Holger Jannasch at the Woods Hole Oceanographic Institution between 1984 and 1998 were identified and partially characterized by Denaturing Gradient Gel Electrophoresis, 16S rRNA gene sequencing, and by growth tests at different temperatures and on different organic carbon and nitrogen sources. All strains were members of the genera Thermococcus and Pyrococcus. The greatest phylogenetic diversity was found in strains from a single Guaymas Basin core isolated by serial dilution from four different depth horizons of heated sediment incubated at the corresponding in situ temperatures. In contrast, geographically distinct vent locations and sample materials yielded a lower diversity of isolates when enriched under uniform temperature regimes and without prior dilution of the source material.