Several extremely halophilic coccoid archaeal strains were isolated from pieces of dry rock salt that were obtained three days after blasting operations in an Austrian salt mine. The deposition of the salt is thought to have occurred during the Permian period (225-280 million years ago). On the basis of their polar-lipid composition, 16S rRNA gene sequences, cell shape and growth characteristics, the isolates were assigned to the genus Halococcus. The DNA-DNA reassociation values of one isolate, strain H4T, were 35 and 38% with Halococcus salifodinae and Halococcus saccharolyticus, respectively, and 65.8-67.8% with Halococcus morrhuae. The polar lipids of strain H4T were C20-C25 derivatives of phosphatidylglycerol and phosphatidylglycerol phosphate. Whole-cell protein patterns, menaquinone content, enzyme composition, arrangements of cells, usage of carbon and energy sources, and antibiotic susceptibility were sufficiently different between strain H4T and H. morrhuae to warrant designation of strain H4T as a new species within the genus Halococcus. It is proposed that the isolate be named Halococcus dombrowskii, and the type strain is H4T (= DSM 14522T = NCIMB 13803T = ATCC BAA-364T).