Among 3,501 individuals receiving endoscopic examination for the upper digestive tract, 41 were found to have esophageal candidiasis including 17 malignancies, 14 immunological disorders, 4 diabetes mellitus, 7 other underlying diseases and 7 apparently healthy subjects. The diagnosis was made either by brushing of the esophagus or by histological examination of the biopsied specimen. Systemic invasion of fungi was observed mainly in patients with malignancy involving the hematopoietic system, and most of them had been treated by corticosteroids, antibiotics or anticancer agents. Although complications associated with esophageal candidiasis are rare, it is emphasized that those patients with malignancy as well as impared immunity should be carefully examined for esophageal candidiasis, in order to prevent the fungi from developing invasive candidiasis. It should be noted that a few cases of gastric ulcer treated by H2 blocker revealed esophageal candidiasis, suggesting that decrease of gastric acidity might be one of the factors involved in this pathological condition.