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. This study measured the level of Basque and Spanish of fifth-graders (n=586 divided among 167 classrooms) in three program models (Basque taught as a second language--Model A, Spanish-Basque bilingual--Model B, and instruction primarily in Basque--Model D) in 1987; studied factors influencing the learning of the languages; compared the new data with that of 1983-84; and examined the bilingual model in greater depth. (MSE)