Background Stress ulcer prophylaxis (SUP) may decrease the incidence of gastrointestinal bleeding in patients in the intensive care unit (ICU), but the risk of infection may be increased. In this study, we aimed to describe SUP practices in adult ICUs. We hypothesised that patient selection for SUP varies both within and between countries. Methods Adult ICUs were invited to participate in the survey. We registered country, type of hospital, type and size of ICU, preferred SUP agent, presence of local guideline, reported indications for SUP, criteria for discontinuing SUP, and concerns about adverse effects. Fisher's exact test was used to assess differences between groups. Results Ninety-seven adult ICUs in 11 countries participated (eight European). All but one ICU used SUP, and 64% (62/97) reported having a guideline for the use of SUP. Proton pump inhibitors were the most common SUP agent, used in 66% of ICUs (64/97), and H2-receptor antagonists were used 31% (30/97) of the units. Twenty-three different indications for SUP were reported, the most frequent being mechanical ventilation. All patients were prescribed SUP in 26% (25/97) of the ICUs. Adequate enteral feeding was the most frequent reason for discontinuing SUP, but 19% (18/97) continued SUP upon ICU discharge. The majority expressed concern about nosocomial pneumonia and Clostridium difficile infection with the use of SUP. Conclusions In this international survey, most participating ICUs reported using SUP, primarily proton pump inhibitors, but many did not have a guideline; indications varied considerably and concern existed about infectious complications.