In 17 patients in septic shock and in 12 trauma patients (ISS > or = 20) the gastric pHi and systemic oxygen delivery and consumption were measured every 6 h to evaluate the prognostic significance of the pHi and to determine the relationship between the gastric mucosal oxygenation and the systemic oxygen transport parameters. In the trauma patient the initial pHi has a high prognostic significance (mean survivors = 7.38; non-survivors = 7.15; p < 0.05), while in the septic group no patient with a pathologic pHi (< 7, 35) > or = 12 h survived. Since we found no correlation between pHi and systemic oxygen transport parameters, other factors have to be of greater importance for gut mucosal oxygenation.