Fifty-four students were tested at specific time intervals over 10 years to determine best native language (NL) predictors of oral and written foreign language (FL) proficiency and FL aptitude. All participants completed two years of Spanish, French, or German. Each was administered measures of NL literacy, oral language, and cognitive ability in elementary school. A measure of FL aptitude was administered at the beginning of ninth grade and FL proficiency was evaluated at the end of the 10th grade. Among the variables, NL literacy measures were the best predictors of FL proficiency, and NL achievement and general (verbal) intelligence were strong predictors of FL aptitude. Results suggest that indices of NL literacy as early as first grade are related to FL proficiency and FL aptitude nine and 10 years later. Findings provide strong support for connections between L1 and L2 skills, and for speculation that "lower level" skills in phonological processing are important for written language development and oral proficiency in a FL. Appended are: Lists and descriptions of the NL measure and FL aptitude test. (Contains 4 tables.)