The elastic modulus and the viscous modulus of hydrated and airdried cortical bone were determined. All testing was done on highly organized specimens from the human femur with the same specimen loaded alternately in axial tension and compression. Sinusoidal strain rates in the physiologic range were employed. Specimens at 0. 30 and 45 to the long axis of femur were tested to demonstrate directional changes in the moduli. Both moduli showed no change of value in tensile and compressive loading modes.