Some studies on the superficially infiltrated cancer, so-called early cancer, are reported. When the patients had vague sensations referrable to the esophagus, X-ray and esophagoscopic examination were performed routinely. Important endoscopic findings of the early esophageal cancers were the small elevation or the shallow depression associated with slight discoloration and uneven surface. When the esophagoscopic findings were questionable, auxiliary methods for the diagnosis such as aimed biopsy and measurement of counts of radioactive phosphorus under direct vision through the esophagofiberscope, were thought to be very useful.