The Gram-positive coryneform bacteria strains 14g and 7C were found to be able to grow with N2 as sole nitrogen source when incubated under microaerobic conditions. Nitrogenase activity in whole cells was assayed by acetylene reduction. High rates of ethylene production (50–120 nmole/hxmg cell protein) were observed in N2 or glutamate grown cell suspensions shaken in an atmosphere of 2.5% O2, 10% acetylene and 87.5% argon.