Part of a larger research project, this longitudinal study analyzed differences between effective and ineffective high school and college language learners and changes in strategy uses over time. Related studies include a descriptive study, which identified learning strategies used in studying foreign languages, and a course development study, in which foreign language instructors teach their students to apply learning strategies. The longitudinal study was conducted during years 2 and 3 of the project with 55 high school students enrolled in Spanish and 25 college students enrolled in Russian. Findings to date indicate that effective students (50) and ineffective students (30) Spanish or Russian tend to use similar strategies to perform language tasks but that effective students are likely to use a wider range of strategies, as well as a greater number of strategies. Examples of metacognitive strategies include self-monitoring, self-evaluation, selective attention, problem identification, and planning; cognitive strategies include using resources, elaboration, note-taking, making inferences, summarizing, translation, deduction, and substitution. However, qualitative differences were found in the way that effective versus ineffective students applied learning strategies, with the effective learners appearing to use more "on-target" strategies and seeming to be more purposeful in their strategy use and in matching strategies to tasks. Appendices present samples of student workbook pages, tables of frequency of strategy use by Spanish students, and reading proficiency guidelines. Contains 41 references and 33 exhibits. (LB)