This thesis is a study of sibling play and language sociaIization. The concept of language socialization is defined as socialization through language as well as socialization to use language (Schieffelin and Ochs 1986). Fieldwork was carried out for 15 months in a small, Quichua-Spanish bilingual, agricultural community in the central highlands of Ecuador. The lack of land and the desire for change have motivated many men to migrate to the coast and to the major cities of the sierra, striving for upward mobility and economic success in the Ecuadorian society. Lately, however, after the recent takeover of two haciendas, it has been possible for the comuneros to remain in the community. The main focus was on 4 children (2-3 years of age) and their interactions with their siblings and parents. The study is a presentation of their everyday lives, and is based on microanalyses of children's play, parent - child interaction, sibling caretaking and children's work. A San Nicohis developmental story is presented. It was clear that the siblings - hence not only the mothers - were in charge of the young children during much of the day. Siblings are, moreover, often raised in pairs, so that an elder child is in charge of a younger one. Threats, rhetorical questions and other types of teasing were conunon means used by adults as well as older siblings to socialize young children. Also very small children were able to take the perspective of their younger siblings. They functioned as interpreters in "language teaching", in so-called diga routines, and in ente,1ainments. In this highly gendered society, the children's play transcended gender boundaries. For instance, young boys were observed"breastfeeding" their young siblings. A language shift ft'om Quichua to Spanish is apparently under way in the community. The comuneros themselves are at a loss to understand or explain why this is happening and, above all, why this is happening now. They do not see the Quichua language as endangered, since they see it as innately Indian. Contrary to what the comuneros initially claimed, it was found that no children under the age of 10 were fluent in the vernacular. Sibling caretaking is possibly one of the most important factors explaining this language shift in their children's lives.