Upper gastrointestinal bleeding in dengue fever. Twenty-six virologically and serologically confirmed Dengue patients with signs of upper gastrointestinal tract bleeding (13.1%) were studied during the 1987 outbreak in southern Taiwan. Within a 1-yr period from 1987 to 1988 in Kaohsiung Chang Gung Memorial Hospital, there were 198 patients with Dengue fever confirmed. Viral isolation and serological studies indicated that type I Dengue was the cause. There was no evidence of sequential secondary infection among them. The 26 patients were evaluated gastroduodenoscopically. Most of the Dengue patients who developed upper gastrointestinal bleeding had gastric ulcers or duodenal ulcers; superficial and hemorrhagic gastritis are the other relevant endoscopic findings. Thirteen patients (50%) had a past history of peptic ulcer symptoms, whereas the other 13 did not. Dengue infection is a precipitating factor in inducing peptic ulcer bleeding because of hemostatic derangements. Supportive therapy and blood transfusions alone were adequate treatment, except for one patient who required surgery due to massive bleeding of a duodenal ulcer. No mortality was observed in this study. 