Reverse differential-pulse voltammetry (RDPV) was studied in order to achieve voltammetric signal resolution for the separate determination of the concentrations of different catechol compounds. Owing to differences in the mechanisms of coupled chemical reactions and in the adsorption character of the species involved significant differences could be observed between the RDPV behaviour of different catechol compounds. The electrochemical and adsorption behaviour of various catechols at electrochemically pretreated carbon fibre electrodes was characterized. In addition to the main in vitro studies, preliminary in vivo voltammetric measurements were also carried out. In particular, the signal separation of norepinephrine and 3,4-dihydroxyphenylacetic acid was studied in the brain of anaesthetized rats.