The U.S. Environmental Protection Agency (EPA) is required to assess the quality of data that are collected in its research and monitoring programs, and this requirement is meant to apply to established areas such as air and water pollution monitoring as well as to the emerging use of geophysics in ground-water investigations. The Agency's quality assurance requirements are outlined, and the ability to meet the requirements in ground-water investigations is discussed. Suggestions are offered on how standards and standard methods can be developed, based upon the experiences obtained in the implementation of monitoring programs in air pollution in the 1970's. The concept of reference and equivalent methods is compared in the monitoring of the air quality with the assessment of ground-water quality for the EPA. The applicability of quality assurance to the many and varied steps in a ground-water investigation is discussed with emphasis given to geophysics. The lack of standard procedures and quality assurance guidelines for geophysical investigations of hazardous waste sites poses serious questions to the acceptance of emerging disciplines for ground-water quality studies.