Host-selective ACTG-toxins A to F have been isolated from the culture broth of a variety of Alternaria citri isolates that cause brown spot disease of the Dancy tangerine (Citrus reticulata) and other mandarin cultivars. However, during investigation of these host-selective toxins, we found that this fungus also produces considerable amounts of nonspecific toxins simultaneously in the culture broth. In this paper we present procedures for the isolation and identification of tentoxin and tenuazonic acid, and the structural assignments for a stereochemically novel dihydrotentoxin (Fig. 1).