This study is concerned with the process of linguistic adoption, in particular the setting up of techniques that can be used to identify adopted material (adoptives) within Bantu languages and especially adoptives that result from the mutual interpenetration of Bantu languages. A model of identification has been set up principally by applying Guthrie's comparative techniques and results to Matengo (N13), a Bantu language spoken in Southern Tanzania. After a background description to the languages involved here and a brief treatment of some of the theories generally held on Lexical Borrowing, in which Swahili loans of non-Bantu provenance have mostly been employed, regular and irregular (skewed) reflexes of Common Bantu 'starred' forms in Matengo have been abstracted, and the skewed reflexes examined to determine whether or not the forms involved are loan suspects. When the irregular reflexes contain extraneous phonological features, whether segmental (Chapter 3) or tonal (Chapter 5), and especially if a possible source language for the skewing or extraneousness can be found, then our suspicion regarding loaning is strengthened. The languages employed in this study as examples of those from which Matengo might have adopted part of its Bantu material are Manda (N11) and Ngoni (N12), close linguistic associates of Matengo, and Standard Swahili (here distinguished from Ki-Unguja - G42d) which has had significant contact with Matengo. The identification methodology developed in this study has also been tested on material unrelated to Common Bantu (Chapter 4) and some putative adoptives of intra-Bantu source have been detected in such material. In this connection, only the segmental features have been taken into account, since the tonal typologies of Common Eastern Nyasa (*EN) have not been worked out.