Motivation is one of the most frequently discussed variables due to its crucial role in successful second or foreign language learning. Several studies have shown the construct of motivation and relationships between motivational components and language achievement. However, it is still unclear whether or not these individual-difference variables can be developed or undermined in a classroom context. In this study, the dynamicity of individual-difference variables during 15-week university English courses in Japan was investigated. A total of seven variables were examined: test and English classroom anxiety, persistence, motivation to learn English, integrative orientation, instrumental orientation, communication apprehension, and cooperativeness. The results indicated that learners' anxiety and their sense of cooperativeness changed significantly, but other variables showed a stabilizing tendency from a global perspective. However, an individual analysis revealed that learners with high motivation showed the upholding of motivational components, whereas learners with low motivation showed the positive development of them. Finally, the decrease in communication apprehension that was assumed to be caused by the increase in cooperativeness led to the disappearance of negative relationships between communication apprehension and motivational variables. (Contains 2 figures and 8 tables.)