The genusAlternaria is responsible for different plant diseases such as tobacco brown spot, tomato blight, and citrus seedling chlorosis but can also be present during storage of grain. The objective of the present paper is to summarize the knowledge concerning regulation of secondary metabolism inAlternaria, particularA alternata (A tenuis). The paper mainly deals with regulation of polyketide biosynthesis, one of the major pathways leading to the biosynthesis of mycotoxins inAlternaria.The mostly studiedAlternaria mycotoxins are dibenzopyrones such as alternariol (AOH) and alternariol monomethyl ether (AME) and altenuene along with the tetramic acid tenuazonic acid.The biosynthesis ofAlternaria mycotoxins has been reviewed by Stinson (12). Most information is available for the biosynthesis of the polyketides AOH / AME while a few biosynthetic studies have been accomplished for tenuazonic acid (11).