Although gastric cancer(GC)is one of the leading causes of cancer-related death,major therapeutic advances have not been made,and patients with GC still face poor outcomes.The prognosis of GC also remains poor because the molecular mechanisms of GC progression are incompletely understood.MicroRNAs(miRNAs)are noncoding RNAs that are associated with gastric carcinogenesis.Studies investigating the regulation of gene expression by miRNAs have made considerable progress in recent years,and abnormalities in miRNA expression have been shown to be associated with the occurrence and progression of GC.miRNAs contribute to gastric carcinogenesis by altering the expression of oncogenes and tumor suppressors,affecting cell proliferation,apoptosis,motility,and invasion.Moreover,a number of miRNAs have been shown to be associated with tumor type,tumor stage,and patient survival and therefore may be developed as novel diagnostic or prognostic markers.In this review,we discuss the involvement of miRNAs in GC and the mechanisms through which they regulate gene expression and biological functions.Then,we review recent research on the involvement of miRNAs in GC prognosis,their potential use in chemotherapy,and their effects on Helicobacter pylori infections in GC.A greater understanding of the roles of miRNAs in gastric carcinogenesis could provide insights into the mechanisms of tumor development and could help to identify novel therapeutic targets. Although gastric cancer (GC) is one of the leading causes of cancer-related death, major therapeutic advances have not been made, and patients with GC still face poor outcomes. The prognosis of GC also remains poor because the molecular mechanisms of GC progression are incompletely understood. MicroRNAs (miRNAs) are noncoding RNAs that are associated with gastric carcinogenesis. Studies have been made with gastric carcinogenesis of GC.miRNAs contribute to gastric carcinogenesis by altering the expression of oncogenes and tumor suppressors, affecting cell proliferation, apoptosis, motility, and invasion. More over, a number of miRNAs have been shown to be associated with tumor type, tumor stage, and patient survival and therefore may be developed as novel diagnostic or prognostic markers. in this review, we discuss the involvement of miRNA s in GC and the mechanisms through which they regulate gene expression and biological functions. Chen, we review recent research on the involvement of miRNAs in GC prognosis, their potential use in chemotherapy, and their effects on Helicobacter pylori infections in GC. A general understanding of the roles of miRNAs in gastric carcinogenesis could provide insights into the mechanisms of tumor development and could help to identify novel therapeutic targets.