Abstract : Research into human auditory localization acuity and factors that compromise this acuity is an ongoing research program at the U.S. Army Research Laboratory. Although there is a wealth of information in the professional literature about the physical, physiological, and psychological underpinnings of auditory localization, the specific theoretical concepts, localization error metrics, and data collection methodologies found in various books and articles are quite diverse and frequently poorly described, making generalizations and data comparison quite difficult. This report is intended to provide information needed to clarify potential methodological and interpretational issues as well as to describe the state of the art in auditory localization science. The specific issues addressed by the report are (1) a common terminological and methodological framework for information exchange regarding localization acuity, (2) the current state of knowledge regarding human localization ability, and (3) various types of localization tasks, measures of localization accuracy and precision, and methods for handling reversal errors. Due to the angular (directional) nature of localization data, a particular focus of the report is the discussion of both circular (spherical) and linear metrics; the statistical methods of data analysis; and the criteria under which a linear analysis of localization data is justified.