Glassy carbon (GC) is one of the most often used carbon materials in laboratory practice. Despite the fact that its electrocatalytic properties are largely surface-state dependent, a standardised procedure for its activation is lacking. This work presents a detailed, systematic investigation of aGC electrode pre-treatment based on potential cycling in a strongly alkaline environment within optimised potential limits. The surface composition was followed by X-ray photoelectron spectroscopy. This allowed determination of the overall elemental surface composition as well as identification of important surface functional groups. Electro-catalytic activity of the activated electrodes was tested by using Fe3+/2+, Fe(CN)(6)(3-/4-) and benzoquinone/hydroquinone couples. A combination of spectroscopic and electrochemical information made it possible to establish a correlation between the electrode's electrocatalytic activity and its surface composition and to identify optimal activation conditions which resulted in a highly active, reproducible and stable electrode surface. It can be concluded that, due to its relative simplicity and efficiency, the present method has the potential to become a standard procedure of GC electrode activation. (C) 2019 Elsevier Ltd. All rights reserved.