Purpose: To examine the predictive validity of the Language Use Inventory (LUI), a parent report of language use by children 18-47 months old (O'Neill, 2009). Method: 348 children whose parents had completed the LUI were reassessed at 5-6 years old with standardized, norm-referenced language measures and parent report of developmental history. The relationship between scores on the LUI and later measures was examined through correlation, binary classification, and receiver operating characteristic curve analysis. Results: For children aged 24-47 months at the time of LUI completion, LUI scores correlated significantly with language measure scores. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were also calculated for 4 cutoff scores on the LUI, including -1.64 "SD", a score that maximized sensitivity to 81% and specificity to 93%. For children aged 18-23 months at the time of LUI completion, specificity and NPV were high, but sensitivity and PPV were lower than desirable. Conclusions: The results provide initial support for the LUI's predictive validity, particularly for children 24-47 months, and suggest the LUI can serve as an indicator of later language outcomes in referred populations. The results compare favorably to findings for other early child-language measures.