Three techniques, constant-potential amperometry, high-speed chronoamperometry, and fast-scan cyclic voltammetry, have been used extensively to investigate the rapid events associated with neurotransmission. These techniques vary in sensitivity, chemical resolution and temporal resolution. Amperometry provides the best temporal resolution but little chemical resolution. Fast-scan cyclic voltammetry provides both good temporal and chemical resolution, while high-speed chronoamperometry offers good temporal resolution and moderate chemical resolution. The amount of chemical information which is needed for a neurochemical measurement depends upon the sample. For single cells, secondary methods, such as HPLC and capillary electrophoresis, offer extensive chemical information about the contents of a cell. With this information, chemical information is not needed during the electrochemical measurement. Therefore, amperometry is employed to obtain the greatest temporal resolution. However, when using more complex biological samples, such as brain slices or in vivo implantation, there is a greater demand for chemical resolution provided by the electrochemical measurement. To bolster results, further confirmation is sought from anatomical, physiological and pharmaceutical evidence. Within this review, the three electrochemical techniques are outlined and compared. Examples are then provided of measurements which have been made in the three predominant biological samples which have been studied: single cells, brain slices and intact animals.