Voltammetric/amperometric microelectrodes are well established in electroanalysis. Their dimension is usually in the range of micrometers and less. They may have very different shapes and may work in the form of assemblies. The most popular are microdisk‐ and microcylindrical electrodes. The unique properties of microelectrodes have allowed analysts to create new analytical methods and procedures. On the other hand they can also be used successfully in the areas where regular electrodes dominated for years. It is relatively easy to get steady‐state currents while working with microelectrodes. This feature appeared to be particularly useful in electrochemistry and, in general, in physicochemical investigations. The theory of voltammetry and amperometry with microelectrodes is well developed. This article focuses on the formulas that can be employed while working with microelectrodes under a variety of conditions including the mixed diffusional and migrational transport.