Mycotoxins are fungal poisons. This definition does not stipulate whether fungi are the targets of poisoning or are the producers of the poisons. The following is suggested as a useful working definition: Mycotoxins are natural products produced by fungi that evoke a toxic response when introduced in low concentration to higher vertebrates and other animals by a natural route. Some mycotoxins have multiple effects, and may cause phytotoxic and antimicrobial syndromes in addition to animal toxicity. By convention, mushroom and yeast poisons are usually excluded from discussions of mycotoxins. The eclectic nature of the discipline and the international scope of the problem has attracted scientists from many different backgrounds. The publishers and editors of Mycopathologia intend for this journal to become a major forum for mycotoxin research.