This retrospective study examined L1 achievement, intelligence, L2 aptitude, and L2 proficiency profiles of 208 students completing two years of high school L2 courses. A cluster analysis was performed to determine whether distinct cognitive and achievement profiles of more and less successful L2 learners would emerge. The results of nonhierarchical ("k"--means clustering) revealed three distinct cognitive and achievement profiles. Participants in the high-achieving cluster scored above average range generally on all L1 and L2 measures; students in the average-achieving cluster scored average range generally on all L1 and L2 measures; and those in the low-achieving cluster scored low to below average range generally on all measures except IQ. Findings suggest that students' level of achievement in L1 skills developed prior to L2 exposure is strongly related to and consistent with their L2 aptitude and proficiency, level of attainment in L2 is moderated by level of attainment in L1, and L2 learning runs along a continuum of learners with stronger to weaker language skills. (Contains 3 tables and 5 figures.)