Rickets and osteomalacia may result from a wide spectrum of inherited and acquired metabolic abnormalities which produce sufficient decrease in serum calcium, phosphate, or both to impair mineralization of the skeleton and epiphyseal growth. Although these various abnormalities may cause strikingly similar findings in affected patients, the respective diseases can usually be separated and identified by careful evaluation of the clinical, roentgenographic, and laboratory data. The prognosis and treatment may vary considerably depending on the cause of the rickets or osteomalacia. Each patient must be carefully studied and treated with the appropriate regimen for his or her particular metabolic abnormality.