A small but significant bacitracin production has been observed in the neotype Bacillus licheniformis ATCC 14580. This strain produces bacitracin only during the phase of rapid growth. The bacitracin production ceases before growth is completed, and the relationship between growth and antibiotic production was not influenced by different environmental conditions. The maximum titre produced by the neotype strain was about 1 i.u. bacitracin/ml. This maximum titre was not influenced by the environmental conditions which resulted in a great variability of the maximum titre of the known bacitracin producer Bacillus licheniformis ATCC 10716. In contrast to B. licheniformis ATCC 10716, the bacitracin production of the neotype B. licheniformis ATCC 14580 was not stimulated by Mn(II)ions. It is suggested that bacitracin may be incidentally overproduced by certain strains grown in certain environments. The controlled bacitracin production by the neotype is not consistent with the definition of secondary metabolites and the hypothesis concerning the function of secondary metabolites after growth of the producer organisms.