Hyphomicrobium species were enriched in media with methanol as sole carbon source under conditions supporting denitrification. Pure cultures of Hyphomicrobium species were isolated which denitrified vigorously with methanol. Hyphomicrobium B522, isolated by aerobic enrichment, was adapted to anaerobic growth and denitrification. Hyphomicrobium B522 and a new isolate were surveyed for anaerobic growth and denitrification on a number of simple organic compounds. Cell suspensions were tested for denitrifying activity. Nitrogen production from nitrate and nitrite and carbon dioxide production from methanol were stoichiometric.