2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, dioxin) represents the prototype for a class of structurally related halogenated aromatic hydrocarbons (HAHs)1-3. These man-made compounds are mostly by-products of industrial processes involving chlorine chemistry and combustion of fuels. Many such chemicals are widespread and persistent environmental contaminants. TCDD is the most potent among the chemicals; animals exposed to TCDD exhibit a wide range of toxic and adaptive responses. Humans exposed to TCDD exhibit certain skin lesions such as chloracne; the possibility that TCDD exposure causes certain neuro- and psycho-pathological alterations, some forms of cancers and diabetic conditions, and reproductive lesions is a particular concern of public health.