||Although nursing care hours (NCH) is commonly used to examine factors related to adverse events among inpatients, the reliability of the NCH measure has rarely been examined. This study assessed the reliability of NCH data from the National Database of Nursing Quality Indicators® by estimating intraclass correlation coefficients (ICCs) with data from the California Office for Statewide Health Planning and Development. Hospital-level aggregated NCH data for critical care units were linked from each of the databases for 48 California hospitals matched in the two databases. Estimated ICCs were .96 for registered nurse (RN) hours and .72 for non-RN hours. Findings provide evidence that NCH data of the national database were substantially reliable for use in national comparable benchmarking reports for hospitals' quality improvement activities and research.