A primary objective of the National Surface Water Survey and, thus, of the National Stream Survey is to ensure that the data collected are scientifically sound and of known quality. An extensive quality assurance program has been established in support of the objective. To evaluate the effectiveness of the quality assurance program, several types of quality assurance and quality control samples were collected and analyzed during a pilot survey that was conducted prior to the initiation of National Stream Survey Phase I field activities. The report presents a statistical analysis of results obtained for field duplicate samples, blank samples, and audit samples used in the pilot survey. The results show that even overall estimated within-batch precision was adequate to meet the analytical data quality objectives established for the National Stream Survey and that detection limit goals were achieved at the contract analytical laboratories. The observed system decision limits and system detection limits, however, must be considered in interpreting the pilot study data and data from future surveys that employ similar sampling, processing, and analytical methods.