Echinulin is a diketopiperazine isolated originally from Aspergillus echinulatus by Quilico and Cardini, University of Florence, Italy in 1943. Echinulin is a unique secondary metabolite with the tryptophan component comprising a triprenylated indole in the 2-, 5- and 7- positions. The high level of prenylation and the “reverse” incorporation of the 2-prenyl group stimulated a large number of articles on the metabolite’s biosynthesis. Echinulin has pulmonary and hepatic toxicity but despite extensive interest, its pharmacology is largely unexplored.