Microdialysis is a method of sampling a liquid compartment by means of a hollow fibre dialysis membrane. The method was developed in the 1980s as a technique for sampling the extracellular fluid of the brain of conscious animals. When used in combination with sensitive analytical chemical tools, microdialysis can be used to study the regulation of neurotransmission in the living brain. Here we describe the application of microdialysis for sampling and detection of biogenic amines (dopamine, noradrenaline and serotonin) in brain tissue. A short overview of the microdialysis technique and its applications are given. In addition, the analytical chemical methods that are currently used to assay biogenic amines in dialysates are briefly discussed.