Naturally occurring quinones which structurally consist of an anthracene-9,10-dione chromophore are important antitumor agents. The anthracycline antibiotics, in particular, doxorubicin, are major chemothera peutic agents. The pluramycins and the ene-diynes antibiotics also show pro i mise as antitumor drugs. The synthetic anthracene-9,10-diones such as mitoxantrone are potent antitumor agents. Analogues related to mitoxantrone have been synthesized and biologically evaluated. Aza and diaza bioisosteres related to the anthracene-9,10-diones have been prepared and evaluated and several of these chemotypes show promise for development as anticancer agents. This review will discuss the discovery of cytotoxic anthracene-9,10-diones and the synthesis and antitumor properties of the related aza and diaza bioisosteres.