Relationship terminologies of an asymmetric prescriptive character are widespread throughout mainland and insular Southeast Asia. Their western limit is marked by the Kachin of northern Burma (Leach 1961:28-53) while their eastern limit is marked by the Mambai people of central East Timor (Figures 1 and 2). Between these limits are such other instances as occur, for example, among the Lamet of Cambodia (Needham 1960), the various Batak groups of Sumatra (Rodgers 1984), and the Rindi of eastern Sumba (Forth 1981). The principal intention of the present paper is to establish the existence of a new asymmetric prescriptive terminology in East Timor, and by doing so provide empirical justification for adjusting the easternmost limits of nomenclatures of this kind. A subsidiary intent is to offer a contribution to current speculations regarding the transformation of relationship terminologies in eastern Indonesia (Guermonprez 1998; Smedal 2002).