This article discusses lexical and grammatical comparison and sub-grouping in a set of closely related Bantu language varieties in the Morogoro region, Tanzania. The Greater Ruvu Bantu language varieties include Kagulu [G12], Zigua [G31], Kwere [G32], Zalamo [G33], Nguu [G34], Luguru [G35], Kami [G36] and Kutu [G37]. The comparison is based on 27 morphophonological and morphosyntactic parameters, supplemented by a lexicon of 500 items. In order to determine the relationships and boundaries between the varieties, grammatical phenomena constitute a valuable complement to counting the number of identical words or cognates. We have used automated cognate judgment methods, as well as manual cognate judgments based on older sources, in order to compare lexical data. Finally, we have included speaker attitudes (i.e. self-assessment of linguistic similarity) in an attempt to map whether the languages that are perceived by speakers as being linguistically similar really are closely related.