It is unclear whether disseminated tumour cells detected in bone marrow in early stages of solid cancers indicate a subclinical systemic disease component determining the patient's fate or simply represent mainly irrelevant shed cells. Moreover, characteristics differentiating high and low metastatic potential of disseminated tumour cells are not defined. We performed repeated serial bone marrow biopsies during follow-up in operated gastric cancer patients. Most patients with later tumour relapse revealed either an increase or a constantly high number of tumour cells. In contrast, in patients without recurrence, either clearance of tumour cells or negative or low cell counts were seen. Urokinase plasminogen activator (uPA)-receptor expression on disseminated tumour cells was significantly correlated with increasing tumour cell counts and clinical prognosis. These results demonstrate a systemic component in early solid cancer, indicated by early systemically disseminated tumour cells, which may predict individual disease development.