The bioelectrical impedance analysis (BIA) method is an attractive tool for use in the clinical assessment of human body composition. Factors such as ease of use, relatively low cost, noninvasive nature, high degree of reproducibility, and safety of operation provide an impetus for the general application of this method. The preponderance of the published applications of BIA focused on applications in healthy populations and indicated a qualitative validity of the method. More recent applications have augmented the quantitative values of the BIA approach and have reported very good specificity and sensitivity. One potential limitation of the BIA approach is the reliance on regression models, derived in restricted samples of human subjects, which restricts the usefulness of the derived model in other patients who differ from the original sample in which the model was developed. Other investigational approaches that use different physical models (bioelectrical impedance spectroscopy and parallel model) have yielded successful and useful measures of human body composition in clinical studies. If BIA is to gain acceptance in clinical diagnosis and evaluation of therapeutic interventions, further efforts will be needed to ascertain more fully the validity, sensitivity, and specificity of biological parameters estimated with the new BIA approaches, and to establish the prognostic values of the BIA estimates of body composition.