Blasticidin S is a nucleoside produced by several species of Streptomyces, first reported in the late 1950s. Blasticidin S is an antifungal agent with particularly potent activity against the rice pathogen, Piricularia oryzae, for which it was used commercially for some time in Japan. Blasticidin S inhibits protein synthesis and is active against bacteria, tumor cell lines and nematodes. More recently, blasticidin S has been used as a marker for strain manipulations. Blasticidin S provided by BioAustralis is presented as the free base to avoid problems associated with the use of the hydrochloride.