An intense discoloration of the gastric mucosa or the gastrointestinal tract found at autopsy gives rise to the question of its cause. Such discolorations are mostly described in the context of intoxications. However, traditional foods and diagnostic procedures using indicator dyes can also lead to an unusual discoloration of the mucous membranes. The authors report on the autopsy findings in a man who died from a bleeding gastric ulcer and whose gastric mucosa showed intense blue discoloration. Experimental postmortem examinations (on stomachs) were performed with methylene blue, a dye used in gastroenterology, resulting in a blue discoloration resembling the appearance of the stomach in the autopsy case. Together with the outcome of the toxicological analyses, the experiments pointed to a diagnostic procedure using methylene blue (chromoendoscopy).