Much research in second language acquisition (SLA) centres on the relationships among individual difference measures such as language attitudes, motivation, anxiety, self-confidence, language aptitude, learning strategies, field independence, and measures of achievement in the language. Numerous studies have supported the proposed influences of these individual difference variables on achievement, and a number of models have been developed to explain the relationships among subsets of these variables. However, there is a lack of research examining the relationships among all these variables simultaneously. In the present study, we investigate a large number of individual difference measures to determine their underlying dimensions, to contrast their predictive validities, and to evaluate their contributions in a causal model of SLA. Our study was based on a sample of 102 university students enrolled in introductory French. The results indicated substantial links among the affective measures and achievement. Support was found for these connections in the proposed causal model.