Despite the reduction in the incidence and mortality of gastric cancer in recent years, it remains one of the most common and lethal malignant neoplasms worldwide. The diagnosis of gastric cancer at an early stage (early gastric cancer) represents the only hope for improving survival of these patients. Upper GI endoscopy (including chromoendoscopy and magnifying endoscopy) remains the corner-stone for diagnosis, although other modalities such as endoscopic ultrasonography, conventional radiographs, computed tomography, magnetic resonance imaging and virtual endoscopy, are helpful. Histology always seals the correct diagnosis, and makes the final staging. The experience of the endoscopist is a critical point related to correct diagnosis. Better awareness by endoscopists of the various appearances of early gastric cancer, is mandatory. In this review, we discuss the epidemiology, biological characteristics and diagnosis of early gastric cancer based on data derived from the currently available literature.