The LLAMA language aptitude test battery (Meara, 2005) has figured in about 50 published studies, but few have directly addressed how well it actually does the job of predicting variance in language acquisition. One way of evaluating the external (criterion-related) validity of an aptitude test is to systematically examine its correlations with learning outcomes. The present chapter reports on a systematic review of previously published correlations between LLAMA and various L2 tasks (e.g., grammaticality judgments, pronunciation, or overall L2 proficiency). The review reveals that although several of the included studies did find significant correlations between LLAMA scores and L2 tasks, samples were often small, and many studies, often those with larger sample sizes, reported ambiguous or near zero correlations with the outcome, and this in cases where positive associations between aptitude and L2 outcomes would theoretically be expected. The review also revealed that the four LLAMA tests have been unevenly represented in research and that more studies using the full LLAMA suite in correlational designs with a variety of L2 outcomes would be desirable in order to evaluate the external validity of the LLAMA. At present, there is a need for caution when researchers base their findings on correlations with LLAMA because too little is yet known about its predictive validity.