This paper proposes a quantitative approach and some brief comments on the ethnolinguistic atlas of the Basque Country carried out by the Aranzadi scientific society (San Sebastian), published in two parts in 1983 and 1990. Measuring lexical variation in a dialectal status language requires a criterion in order to count lexical items. This criterion is not self-evident to determine, particularly when we deal with an agglutinating language whose lexical productivity is a typical feature. We propose here a method for that, and an overall picture of the situation.