This article examines the interrelationship between Aimara, Quechua and Castilian languages in the central valleys of Bolivia, as observed by the author during several fieldwork stories in the 1990s. It is based on the premise that the socio-economic distribution and usage patterns of these languages must be explained in terms of the unequal social, economic and political power relations between the urban sector and the peasant sector at the time. First, the article provides an overview of the macro sociolinguistic landscape, followed by a micro analysis of the influences between the three languages, focusing on a number of lexical fields in particular. Attention is drawn to the interest of taking into account the perspectives of the same speakers in order to characterise the meaning of linguistic contact from an anthropological rather than a purely formal point of view.