A newly isolated strain of Streptomyces lusitanus var tetracyclini NCIB 9500 produces tetracycline with no co-production of chlortetracycline in the presence of Cl-. Thus, in a 6000-1. fermentor, with corn-steep medium contg. 1.5 g. NH4Cl/l. the strain produces 11.1 g. tetracycline/l. and no detectable amt. of chlortetracycline.