In the past 10 years, the management of brain injury has shown several advances. Besides new diagnostic tools many new tentative approaches have been investigated, such as jugular bulb measurement of oxygen and lactate differences and near-infrared spectroscopy. The latest tool is microdialysis, which uses a probe as an interface to the brain. This method uses internally perfused semi-permeable membrane probes, which allow neurochemical water-soluble substances to be collected outside the brain for further analysis. Since the late 1980s the first results of microdialysis in neurointensive care show that chemical substances such as lactate, glucose, amino acids, metabolites of several biochemical mechanisms and electrolytes are measurable. This heterogeneous approach now waits for validation for clinical use and for the most challenging aspect, the clinical interpretation and use to improve therapy. The aim of this review is to describe the state of the art of this new technique, including our own experiences and concepts.