Precision and accuracy data obtained from state and local agencies during 1987 are analyzed. Pooled site variances and average biases which are relevant quantities to both precision and accuracy determinations are statistically compared within and between states to assess the overall effectiveness and consistency in the application of various quality assurance programs. Individual site results are evaluated for consistent performance throughout the year. Reporting organizations, states and regions which demonstrate consistent precision and accuracy data as the result of effectively administered quality assurance programs are identified. This information is intended as a guide for identifying problem areas, for taking corrective action from the standpoint of improving the effectiveness of quality assurance programs, and for providing more knowledgeable decisions concerning attainment status with regards to ambient air quality standards. An approach to deal with accuracy data for individual sites is presented, and an alternative sampling design for generating precision and accuracy data is discussed.