In this study I examine the construct of aptitude in learning Chinese as a second language (L2) to an advanced level. I test 2 hypotheses: first, that L2 aptitude comprises 4 components--working memory, rote memory, grammatical sensitivity, and phonemic coding ability--and second, that L2 aptitude affects learning both directly and indirectly (mediated by strategy use and motivation). Native speakers of English ("n"?=?96) studying advanced Chinese took the Modern Language Aptitude Test and a phonological working memory test and responded to motivation and strategy use questionnaires. Using end-of-course listening, reading, and speaking proficiency test results as measures of Chinese learning, I constructed a structural equation model to test the hypotheses. The model fit the observed data. Of the 4 components foreseen to comprise L2 aptitude, rote memory contributed the most and working memory the least. Aptitude, strategy use, and motivation had about the same impact on learning but varied in how well they predicted the individual skills of listening, reading, and speaking. The results shed light on L2 aptitude in the particular context of an advanced L2 Chinese course. (Contains 2 figures, 1 table, and 9 notes.)