This study on Basque language learning is part of a project investigating alternative curriculum designs to promote native language maintenance in the Basque Country of Spain. The study measured the level of Basque and Spanish language proficiency in second- and fifth-grade students in three bilingual education program designs (Basque taught as a second language--Model A, Spanish-Basque bilingual--Model B, and instruction primarily in Basque--Model D); analyzed psycholinguistic, sociolinguistic, and other factors in teaching Basque; obtained specific quantitative and qualitative information on the educational system's language situation in the 1983-84 school year; developed methodology and instruments for the research; and created and developed instruments for measuring and evaluating language competence. (MSE)