We describe the histamine actiuity of Bacillus macerans 1(3), isolated from a sample of Italian cheese during seasoning. Bacillus macerans 1(3) did not hydrolyse gelatine, and had a clear positive indol production. On the other hand we have observed growth with 5% NaCl concentration and with pH = 5. This is a halotolerant bacteria. Strain 1(3) has a positive reaction in Niven medium at 24 and 48 h. A histamine formation was detected at all temperatures studied (43, 37, 30, 22 and 4°C). The maximum histamine formation and the maximum bacterial growth were detected at 30°C, with 4285 μg of histamine ml-1 of quantification broth. © 1994 Academic Press Limited.