This study was performed on a sample of 1,276 part-time (PT) and full-time (FT) Language Learning Center (LLC) students enrolled in French, Spanish, German and Russian during FY67-74. The study sought to: (1) develop a statistical data base for use in future curriculum and testing studies; (2) examine factors affecting language learning success; and (3) to compare French, Spanish, German, and Russian training in terms of student body and instructional effectiveness. Findings include: (1) FT and PT students within each of the four languages have significantly differing psychological and linguistic profiles; (2) PT training is more effective than FT training for exit proficiency goals of S-1 and S-2; (3) the number of hours needed to attain S-1 and S-2 is significantly influenced by measured language aptitude; (4) the number of hours needed to attain S-2 is significantly influenced by prior language training; and (5) each of the four languages requires a different combination of factors to optimize the prediction of exit proficiency and improvement. Appendices contain: psychological measures; sample Modern Language Aptitude Test; language proficiency rating criteria; and tables and figures. (Authors/AM)