We previously proposed a clinical state of metastasis termed 'oligometastases' that refers to restricted tumor metastatic capacity. The implication of this concept is that local cancer treatments are curative in a proportion of patients with metastases. Here we review clinical and laboratory data that support the hypothesis that oligometastasis is a distinct clinical entity. Investigations of the prevalence, mechanism of occurrence, and position in the metastatic cascade, as well as the determination of molecular markers to distinguish oligometastatic from polymetastatic disease, are ongoing.