Though the Tsimihety tribe is the subject of three monographs by Molet (1953, 1956, 1959) and a number of papers by various authors (e.g. Mattei, 1938; Magnes, 1953), its social structure has not yet been adequately described. Indeed, there is no adequate account of the social structure of any Malagasy group, although Ottino's (1963) analysis of aspects of Vezo social structure is very illuminating. The primary aim of this paper therefore is to describe two of the major features of Tsimihety social structure—kinship and descent. As there are facets of Tsimihety kinship and descent that have some bearing on recent discussion of these topics, a secondary aim is to contribute, in a minor way, to that discussion.