A large number of iron transport agents, siderophores, which stimulated the growth of Arthrobacter flavescens JG-9, were isolated during a study of the antitumor activity associated with the metabolic products of the fungus Epicoccum purpurascens. The production of the siderophores was significantly enhanced in a variety of media by culture of the fungus in the near absence of ferric iron. A novel method of purification involving a carboxylic ion-exchange resin separated the siderophores into four subgroups. The first subgroup, which contained the majority of the activity, was subsequently resolved in a similar manner with the carboxylic resin into seven individual siderophores. Of these, two were characterized as ferricrocin and coprogen whereas the others appeared to represent new compounds. One of the latter was given the name triornicin and exhibited slight antitumor activity in mice injected with Ehrlich ascites tumor cells.