In an attempt to elucidate the etiology and pathogenesis of 'Itai-Itai' disease, the relationship between bone and kidney lesions in cadmium-poisoned rats was determined using the standard renal clearance technique. Calcium and cadmium contents in the femur and kidney were also estimated. The severity of renal lesions was histologically evident both in the tubule and glomerulus, and paralleled the decrease in GFR and the increase in FF. There was no significant change in fractional excretion of phosphate, but fractional excretion of calcium increased in the cadmium-poisoned rats. The secondary hyperparathyroidism followed by uremic renal osteodystrophy did not result in an osteomalacia. Thus, it is apparent that disturbance in calcium reabsorption in the tubules plays a role in the loss of calcium, and cadmium associated with low levels of calcium has a direct effect on the bone-causing osteomalacia.