Abstract: The unique system of the present invention provides an accurate valid measaurement of human body composition consisting of fat tissue, lean tissue and body water. The inventive methodology provides a procedure for quantitative measurement of the conductive potential of the body, which is based on the lean tissue content of the body, in a convenient and reliable manner. In more detail, the quantitative measurement in accordance with the present invention is referred to as a "bio-impedance signal." This electrical signal, in ohms, is derived from a means for measuring body impedance component of the system. The resultant signal (three digit number, between 1 and 1000 ohms) is then entered into a modifying means component to accurately predict the body composition of the tested individual. The unique modifying means, in one embodied form, comprises prediction formulas derived from biological data inputs including: a patient's height, weight, age and sex, to determine a "population prediction variable.