Oncogenous or tumor-induced rickets is recognized as Vitamin D-resistant hypophosphatemic rickets that heals after excision of a coexisting tumor in either bone or soft tissue. Its pathogenesis is not clarified, but it has been suggested that the tumor elaborates a homoral substance inhibiting tubular reabsorption of phosphate or that the tumor inhibits the synthetic process of 1, 25-dihydroxcholecalciferol. We present two cases of vitamin D-resistant rickets, one associated with intrasseous well-differentiated osteosarcoma in the pelvis and the other associated with fibrosarcoma of distal femur. The case with low grade osteosarcoma showed immediate improvement of rickets after excision of the tumor, but the case with fibrosarcoma showed no improvement after amputation and was fatally terminated 5 months later due to lung metastasis.