Standardization of measurement conditions is essential for obtaining accurate, precise, and reproducible bioelectrical impedance analysis (BIA) data. Errors due to lack of measurement control are propagated in subsequent calculations of body composition and contribute to differences in predictive equations among investigators. Various individual and environmental factors have been shown to influence BIA. We review the factors that have been identified from the literature as being conditions requiring standardization both for healthy subjects and for those in a medical setting.