In small capacitance tunnel junctions charging effects can play a significant role or even dominate the tunneling behavior. For a complete description the electrodynamics of the environment have to be taken into account in a proper quantum‐mechanical way. For planar junctions this is now well understood. For STM‐type junctions the situation is less clear. Several experiments will be described which shed some light upon this problem, and the consequences for normal STM operation will be discussed.