Every language includes layers of lexical and grammatical elements that entered it at different times in the more or less distant past. Hence, for periods preceding our earliest historical documentation, linguistic stratigraphy—the systematic study of such layers—may yield information about the prehistory of a given tradition of speaking in a variety of ways. For instance, irregular phonological reflexes may be evidence of the convergence of diverse dialects in the formation of a language, and layers of material from different source languages may form a record of changing cultural contacts in the past. In this volume are discussed past problems and current advances in the stratigraphy of Indo-European, African, Southeast Asian, Australian, Oceanic, Japanese, and Meso-American languages.