Haematologic disturbances in 13 cases of gastric cancer are described. All the patients had anemia of different origin. Increased leukocytosis was observed in half of the cases, leukaemia reaction in one third. Haemolysis was present in 50% of cases. Thrombocytopenia coexisted most frequently with disseminated intravascular coagulation in 4 patients. Bone metastases were visualised as osteolytic foci with radiological methods or increased capture of isotopic marker in the bones under scintigraphic examination. Under the microscope neoplastic metastases were found in bone marrow smears of 5 patients. All patients displayed symptoms of gastric ulcer disease acute or chronic phase. In some cases only repeated gastroscopic examination and mucosa biopsy was the only way to confirm cancer. In other cases the diagnosis was made after the histopathologic examination of the resected stomach, in still others by a section.