Purpose: In this study, the authors examined the diagnostic accuracy of a composite clinical assessment measure based on mean length of utterance (MLU), lexical diversity (D), and age (Klee, Stokes, Wong, Fletcher, & Gavin, 2004) in a second, independent sample of 4-year-old Cantonese-speaking children with and without specific language impairment (SLI). Method: The composite measure was calculated from play-based, conversational language samples of 15 children with SLI and 14 children without SLI. Scores were dichotomized and compared to diagnostic outcomes using a reference standard based on clinical judgment supported by test scores. Results: Eleven of 15 children with SLI and 8 of 14 children with typical language skills were correctly classified by the dichotomized composite measure. The measure's sensitivity in this second sample was 73.3% (95% confidence interval [CI] 48%-89%); specificity was 57.1% (95% CI 33%-79%); positive likelihood ratio was 1.71 (95% CI 0.87-3.37); and negative likelihood ratio was 0.47 (95% CI 0.18-1.21). Conclusions: The diagnostic accuracy of the composite measure was substantially lower than in the original study, suggesting that it is unlikely to be informative for clinical use in its present form. The value of replication studies is discussed.