Over the last 20 years there has been increasing interest in the pivotal role of the splanchnic region in the development of SIRS, sepsis and multiple organ failure. One key question is how to monitor and detect in good time regional splanchnic perfusion, oxygenation and impaired function of liver and gut, so as to start appropriate therapeutic measures. This review describes the pathophysiological background of impaired splanchnic perfusion. It focuses on the advantages and risks of methods of monitoring splanchnic perfusion or oxygenation and considers them regarding clinical relevance and usefulness. Special emphasis is laid on gastric tonometry. Despite all the restrictions and the criticism which can be levelled at this method, it remains the only way of monitoring splanchnic perfusion and oxygenation that is currently applicable in clinical routine. The data gained can be useful if clinicians are aware of the weak points of tonometry and consider the data in the overall clinical picture. When this is done, the patient can profit from gastric tonometry and the benefits outweigh the risks.