This paper examines some experimental evidence relating to the influence of second language learning on native language performance, including results from elementary school Latin programs, research on bilingualism and intellect, and elementary school programs in modern languages. Some studies of Latin FLES programs show that specially designed Latin curricula appear to improve English language arts test scores, although results are not always statistically significant. Studies in bilingual, immersion, and language-switch programs appear to have only marginal relevance, since determining variables are usually sociological, economic, or political rather than linguistic. Also, the difference between learning a language in a communicative setting as opposed to the traditional foreign language classroom must be accounted for. Studies comparing English language arts scores of French and Spanish FLES students with scores of non-language learners are not conclusive; those indicating a positive impact are susceptible to criticism. More conclusive evidence concerning the influence of foreign language study on native language usage will be provided only by a longitudinal study which takes into account I.Q., English ability before taking foreign language, socioeconomic status, language of the home, experience abroad, high school curriculum, language studied, and grade received. Tabular data are included. (EJS)