The antibiotic anthelmycin was first isolated by Hamill and Hoehn from culture filtrates of Streptomyces longissimus. Anthelmycin (hikizimycin) has also been isolated from the fermentation broth of Streptomyces sp., strain A-5 which was obtained from a soil sample collected at the Hikizi river-side, Kanagawa Prefecture, Japan, by Uchida K. et al. Anthelmycin (hikizimycin) is active against fungi, especially phytopathogenic fungi. The drug inhibits the growth of a number of prokaryotic and eukaryotic organisms and also has antihelminthic activity. Anthelmycin inhibits protein synthesis on both pro- and eukaryotic ribosomes by preventing the peptide bond-forming reaction. The drug is structurally similar to certain other 4-aminohexosyl cytosine antibiotics including blasticidin S, gougerotin, amicetin and bamicetin although unlike these compounds anthelmycin lacks an aminoacyl moiety. It is proposed that anthelmycin inhibits the ribosomal peptidyl transferase centre by associating with a site that overlaps the (related) ribosomal receptor site(s) for the other four inhibitors.