During A routine diagnostic x-ray examination a certain amount of direct or scattered radiation will reach the active bone marrow and the gonads. In order to measure this, a phantom of unit density Presdwood, containing a wax impregnated skeleton and lung simulated with cork, was constructed. For measurement of the dose at various points in the phantom, special condenser ionization chambers have been developed with relatively wave-length-independent properties in the energy range of diagnostic x-rays. The design, construction, and properties of these chambers will be described. Preliminary measurements of bone, skin, and gonadal dose for postero-anterior chest and anteroposterior lumbar spine examinations will be presented. From these results an estimate has been made of the average active bone-marrow dose and the integral dose received by the active marrow for the radiographic procedures mentioned above. For these preliminary measurements calibrated commercial ionization chambers were used, since our own...