From the numerous reports in the literature on hypernephromas, it is apparent that much confusion exists concerning both the clinical course and the pathologic variations. It is commonly believed that the hypernephroma is a highly malignant tumor and runs a rapid course. Such a concept is at variance with our findings. We have studied a group of forty-four instances of hypernephroma observed at the Montefiore Hospital, in which autopsies were obtained in thirty-three. In the remainder, pathologic diagnoses were based on the examination of removed kidneys or on biopsies from metastases. Of this group, twenty-eight showed clinical manifestations of neoplasm. In the remaining sixteen, a hypernephroma was discovered as an accidental observation at autopsy. Such tumors were limited solely to a kidney or a suprarenal gland. The patients in this group presented no clinical evidence of a hypernephroma, and all died of other unrelated diseases in which the tumor played