Granulocyte-colony stimulating factor (G-CSF)-producing gastric cancer is a rare disease with a very poor prognosis. A case of this disease that recurred rapidly and progressed is presented. A 76-year-oldmanwhohadepigastricpainwasadmittedtoourhospital.Uppergastrointestinalendoscopy andbiopsyshowedatumorof5.0cmormore,apoorlydifferentiatedadenocarcinoma(por).Abdominal enhancedcomputedtomography(CT)showedagiantmassof7.0cmonthewallofthelessercurvature andmultipleenlargedlymphnodesaroundthestomach.Thepreoperativelaboratorydatashowedleuko-cytosisandahighserumG-CSFlevel(1,010pg/ml).Therewerenoapparentsourcesofinfectionorblood diseases.AG-CSF-producinggastriccancerwassuspected,andtotalgastrectomywasperformed.Pathologicalfindingswerepor,pT4a(SE),pN1,M0,andStageIIIA.ThetumorcellswerepositiveonG-CSF immunological staining. Postoperatively, the leukocyte count improved once, but it then gradually increased.Onpostoperativeday(POD)19,abdominalenhancedCTshowedtwolow-densitymasses,one largerthan5.0cminthebodyofthepancreasandone3.0cminthetailofthepancreas.Themassessuspectedtobeabscessesenlargedgradually,andrecurrenceoftheG-CSF-producinggastrictumorwasdiagnosed.S-1+trastuzumabtreatmentwasstartedonPOD25.ThepatientwasdischargedonPOD34, butdevelopedcardiopulmonaryarrestonPOD36.