We have recently discovered a complex of new isotetracenone group antibiotics, rubiginones, in our screening for vincristine (VCR)-induced cytotoxicity potentiators1*. In the continuation of the screening program, an actinomycete strain Q576-2 identified as Streptoverticillium aspergilloides, was found to produce a new active substance. Isolation and chemical studies of the responsible substance designated piperafizine showed that it was a complex of two components A and B structurally classified in the diketopiperazine family. This note presents a brief discussion of the producing organism, production, isolation, chemical properties and biological activities of piperafizines A and B.