A procedure for the fabrication of carbon disk electrodes with tip diameters approaching 100 nm is described. In this procedure, quartz capillaries are initially pulled down to a small tip by a horizontal micropipet puller. A high gas pressure (900 kPa) is then applied to force methane gas through the pulled capillary while it is being pyrolyzed. A prolonged pyrolysis duration (4 min) is employed to form a carbon deposit at the tip of the capillary in order to construct a carbon disk electrode. Electrical contact is then made between the carbon deposit and a nichrome wire via a small pool of mercury inside the capillary. Hence, unlike the construction procedures for many other microelectrodes, there is no epoxy sealing, cutting, or beveling of electrodes needed in the fabrication procedure for ultrasmall carbon disk electrodes. The fabricated electrodes are then characterized by cyclic voltammetry in a dopamine solution, showing a well-defined sigmoidal response for the oxidation of dopamine with minimal background charging current The absence of epoxy resin at the tip of carbon disk electrodes also permits electroanalysis in nonaqueous media.