Purpose: The purpose of this study was to examine the reliability of, and sources of variability in, language measures from interviews collected from young school-age children. Method: Two 10-min interviews were collected from 20 at-risk kindergarten children by an examiner using a standardized set of questions. Test-retest reliability coefficients were calculated for 8 language measures. Generalizability theory (G-theory) analyses were completed to document the variability introduced into the measures from the child, session, sample length, and topic. Results: Significant and strong reliability correlation coefficients were observed for most of the language sample measures. The G-theory analyses revealed that most of the variance in the language measures was attributed to the child. Session, sample length, and topic accounted for negligible amounts of variance in most of the language measures. Conclusion: Measures from interviews were reliable across sessions, and the sample length and topic did not have a substantial impact on the reliability of the language measures. Implications regarding the clinical feasibility of language sample analysis for assessment and progress monitoring are discussed. (Contains 1 figure and 3 tables.)