Candida is the most common infection of the esophagus, but may infect any level of the GI tract; in fact, some authors believe, based on autopsy studies, that Candida infection of the gastrointestinal tract is increasing in frequency. Common risk factors for invasive Candida infection include immunosuppression, chemotherapy, corticosteroids, and major abdominal surgery. The gastrointestinal tract is a major portal for disseminated candidiasis, since Candida often superinfects ulcers that develop from other causes. It is important to morphologically differentiate between invasive candidiasis and superficial colonization, as Candida is capable of colonizing benign ulcers and mucosal surfaces without invasion. C. albicans is most commonly isolated, but C. tropicalis and C. (Torulopsis) glabrata may produce similar clinical and pathologic manifestations. In addition, other non-albicans species (such as C. krusei and C. parapsilosis) are emerging as important causes of invasive fungal infection.