The tellurides represent a class of compounds which exhibit a wide range of physical and chemical properties. In addition to the salt-like compounds, some tellurides show metallic properties while others have strong covalent bonds. Like tellurium itself, many of these are semiconductors, e.g., the 11-VI compounds CdTe and MnTe, and in this respect are of special interest. Other tellurides, e.g., NbTe, and ZrTe,, have low-dimensional electronic transport properties. Some ternary transition metal-main group metal tellurides appear in an amorphous state with spin glass properties. The tellurium-rich tellurides are characterized without exception by directed Te-Te bonds. It turns out that general structural chemical relationships exist between them which allow these different compounds to be treated as a single comprehensive class of substances. They represent a link between the Zintl phases on the one hand, and molecular compounds on the other.