A study investigated the degree to which first language ability was associated with successful English-as-a-second-language acquisition in 33 outstanding Indonesian teachers. It examined the applicability of theories of common underlying proficiency in the storage of two languages and the development of cognitive academic language proficiency. The teachers had been selected to participate in a master's program in teacher education sponsored by the World Bank. Before beginning the program, the teachers attended three months of training in English for special purposes (ESP) and took sheltered courses in pedagogy for six weeks. After the initial ESP course, the participants underwent a series of tests including English language tests and a test of inferential ability. After the sheltered courses, the teachers' grades were analyzed. Results suggest that while strong first language inferencing ability is associated with better second language ability, English language proficiency is a more salient variable in determining foreign students' grade performance. Several interpretations of the results, relating to both the theoretical models and the tests used, are suggested. Additional cultural orientation for foreign students is recommended. (MSE)