The forces acting in the abductor muscles and on the head of the femur have been determined experimentally for three subjects in a range of different pelvis attitudes. The position of the centre of gravity of the body was determined by force measurement with simultaneous radiography to relate it to the skeleton. The forces were calculated using muscle positions obtained by dissection and radiography of a specimen. Pelvis angle and the position of the trunk and limbs have a considerable effect on the forces. With the pelvis in the normal walking attitude and the limbs symmetrically disposed, muscle forces range from 1.0 to 1.8 and joint forces from 1.8 to 2.7 times body weight.