on three lines of clinical evidence: spontaneous regression, solitary metastases, and delayed metastases. The documentation of curable metastases is most common in hypernephroma and provides the setting to discuss the general problem: are metastases curable? Spontaneous Regression.\p=m-\The recent publication of two monographs on the subject of spontaneous regression of cancer22,38 records the factual data. Of 176 cases of documented spontaneous regressions, 31 cases of hypernephroma were collected, 28 of which had pulmonary metastases.22 Regression followed nephrectomy in 22 of these patients.The definition of spontaneous regression of cancer which is offered as "partial or complete disappearance of malignant tumors in the absence of all treatment or in the presence of therapy which is considered inadequate to exert a significant influence on neoplastic disease." It is not synonymous with cure. As Goodwin has noted in this series, it is based on presumptive radiologic evidence, most often without patho¬ logic proof, and in many instances, of limited follow-up. Death in most cases described was due to metastases, or métastases were present. Solitary Métastases.-A large number of solitary métastases cured by surgery are secondaries due to hypernephroma. The first long-term survivor of a resected pulmonary metastasis was a patient with hy¬ pernephroma.49 A thorough review of the literature indicated that an iso¬ lated metastasis from hypernephro¬ ma is often a solitary lesion."'" The known incidence of circulating can¬ cer cells clearly indicates that not all cancer cells form métastases. The facts favor the view that host resistance allows only a few of the many circulating cancer cells to form secondaries. The finding of solitary métastases implies the abil¬ ity of hosts to destroy the majority of circulating hypernephroma cells.The arguments in favor of multiple surgical procedures must be viewed against the progress of the metastatic process. Once again, the credit for cure may be due to the host and not to the therapeutic procedure.