Neurofibromatosis (von Recklinghausen) is a curious, often familial disease which in its severe forms is readily recognized by the association of multiple tumors of the peripheral nerves with areas of pigmentation in the skin, so-called café au lait spots. Other features, such as involvement of the central nervous system and the skeleton, are less frequently encountered but are of relatively greater importance to the radiologist. In order to investigate particularly the bone manifestations of this disease, we have reviewed the records and roentgenograms of 127 patients with von Recklinghausen's disease seen at the University of Michigan Hospital in the thirteen-year period between 1934 and 1947. Material derived from this study forms the basis for the present report. Historical Smith in 1849 comprehensively described neurofibromatosis, but failed to recognize the nerve-sheath origin of these multiple tumors (1). In spite of frequent additional references to molluscum fibrosum in the interim, it was not un...