Body composition measurements vary greatly in degree of measurement difficulty and accuracy. Hydrostatic weighing, chemical dilution or their equivalents were the accepted "gold" standards for assessing fat mass. Dual Energy X-ray Absorptiometry (DEXA) is fast replacing these techniques as the preferred standard. However, these direct measurement techniques require expensive and precise equipment and must be operated by highly trained personnel. For this reason the "Body Mass Index" or "BMI" is being widely used to indicate body composition. The BMI is thought to be reasonably accurate and simply requires body weight and height measurements. Between these two extremes lie the many other approaches and their corresponding algorithms. The discrepancies inherent in these algorithms are discussed. The prediction accuracy of the more popular empirical algorithms is evaluated. These evaluations indicate that a promising approach to body composition measurements is a combination of both BMI and bioelectric impedance measurements. (Contains 2 tables and 3 figures.)