The aims of this study were to assess the reliability and validity of three methods of bioelectrical impedance analysis (based on induction between the hand and foot, between one foot and the other foot and between one hand and the other hand) and the skinfold method, and to construct prediction equations for total body density by examining cross-validity in young Japanese adult males. The participants were 50 Japanese males aged 18-27 years (height 1.72 +/- 0.06 m, body mass 64.9 +/- 9.0 kg; mean +/- s), each of whom was measured twice using each of the four methods. Relative body fat based on underwater weighing was used as the criterion for validity. To construct prediction equations for body density, we used multiple regression analysis, whereby all possible combinations were examined. The reliability of all three bioelectrical impedance methods was high (R = 0.999). Three new prediction equations were constructed for the hand-foot method, foot-foot method and skinfold method. The cross-validity of the equations was guaranteed. The relative body fat calculated using the new equations did not differ from that based on the underwater weighing method.