Montreal high school students studying French as a second language completed a battery of tests including measures of linguistic aptitude, verbal intelligence, and various attitudinal and motivational characteristics. Analysis of the intercorrelations of these tests yielded two orthogonal factors equally related to ratings of achievement in French: a "linguistic aptitude" and a "motivational" factor. It was also found that maximum prediction of success in second-language acquisition was obtained from tests of: verbal intelligence, intensity of motivation to learn the other language, students' purposes in studying that language, and one index of linguistic aptitude. (Author)