Gastric carcinogenesis is a multistep process involving genetic and epigenetic 
alteration of protein-coding proto-oncogenes and tumor-suppressor genes. 
Microribonucleic acids (miR) are a recently-described class of genes encoding 
small non-coding RNA molecules, which primarily act by downregulating the 
translation of target mRNA. It has become apparent that miR are also key factors 
in cancer, playing both oncogenic and tumor-suppressing roles in gastric cancer. 
Recent studies have shown that a substantial number of miR show differential 
expression in gastric cancer tissues, and they are turning out to be just like 
any other regulatory gene. In this connection, miR dysregulation are reported to 
be associated with incidence, early diagnosis and prognosis of gastric cancer. 
Therefore, investigation of the biological aspects of miR dysregulation might 
help us better understand the pathogenesis of gastric cancer and promote the 
development of miR-directed therapeutics against this deadly disease. The aim of 
the present review was to describe the mechanisms of several known miR, 
summarize recent studies on oncogenic miR (e.g. miR-21, miR-106a and miR-17), 
tumor suppressor miR (e.g. miR-101, miR-181, miR-449, miR-486, let-7a) and 
controversial roles of miR (e.g. miR-107, miR-126) for gastric cancer. In 
addition, their potential clinical applications and prospects in gastric cancer, 
such as biomarkers and clinical therapy tools, are also briefly discussed.