A method is presented for measuring accurately the piezoelectric modulus of small areas on the surface of whole dried bone and of specimens cut from dried bone. The results indicate that the ordered matrix necessary for the piezoelectric effect varies from place to place giving rise to regions of positive and negative charge on the surface of the bone. A map of the charge distribution on the surface of a typical femur under load is presented, and a model of the collagen fiber orientation consistent with the known organization of bone is proposed that explains to some extent the variability of the surface charge-load observations.