Published studies relating to whether medicinal stress-bleeding prophylaxis leading to an increase of gastric pH favors the development of bronchopulmonary infections are reviewed. Results from studies in healthy humans, patients with ulcer disease, and patients in the intensive care unit (ICU) clearly show that the risk of gastric bacterial colonization significantly increases relative to increasing gastric pH. Moreover, a drug-induced increase of gastric pH leads directly to gastric bacterial colonization also in patients in the ICU, above all with bacteria typical of the gastrointestinal tract. Comparing the different bacterial spectra of the oropharynx, stomach, and upper small intestine, it becomes clear that the stomach is a reservoir of bacteria independent of the oropharynx and also subject to retrograde colonization due to the duodenogastric reflux. Both by means of microbiological and in particular direct detection procedures, it can be demonstrated that in at least 30-40% of intubated patients a gastropulmonary route of colonization occurs. In patient groups without a medication-induced increase of gastric pH the number of bacteria detected in the tracheal secretion is about 33% less than in the case of conventional stress-bleeding prophylaxis. These findings make it understandable that a highly significant increase in the pneumonia rate is seen in patients receiving pH-increasing stress-bleeding prophylaxis versus control groups without therapy essentially influencing gastric pH. A risk score was developed that allows an easy description of those patients who are at an increased risk of pulmonary infections due to the gastropulmonary route of colonization.