Numerous reactions have been developed over the years which lead to products containing coupled aromatic nuclei. These methods involve many different types of starting materials as well as a variety of mechanisms. Earlier work was concerned mainly with the lower members of the biphenyl series, but the increasing demand for thermally stable materials has resulted in the development of numerous methods for preparation of the higher molecular weight polyphenyls or poly(phenylene)s. Indeed, research into the preparation and properties of these materials has expanded at a remarkable rate during the last decade and is emphasized by the fact that almost 50% of the references cited herein are the results of work carried out since the last major review on this subject was published in 1960 [1]. Less comprehensive reviews [2–4] have since appeared.