For several years a clear trend from the application of classical so-called “single layer” models to attempts to model the ionosphere in accordance to its real three-dimensional nature can be observed (see, e.g., Scherliess et al., 2003; Hernández-Pajares et al., 1999). European Space Agency (ESA)/European Space Operations Centre (ESOC) commenced in 1998 employing a three-dimensional (3-D) model for ionosphere processing (Feltens, 1998; Feltens et al., 1998). This first version of a 3-D model at ESOC model was based on a simple Chapman profile approach, assuming that the vertical component of the ionosphere could be mathematically expressed in terms of a single β-layer Chapman profile function. The profile function's parameters, maximum electron density N0 and its height h0, were in turn expressed as surface functions of geomagnetic latitude and local time whose coefficients were estimated. In this way a horizontal variation of N0 and h0 was modeled, and the profile function varied vertically, depending on the actual N0 and h0 values at a certain location. The ionosphere, however, consists of several layers. Additionally, the plasmasphere on top of the ionosphere must be accounted for, and the scale height, needed to compute the profile function z-parameter, is height-dependent. Furthermore, some of the ionosphere layers are so called α-layers and some parts of the ionosphere show special behavior. All these effects must be accounted for in a proper 3-D mathematical modeling. It is the intent of this paper to give a substantial overview over the 3-D ionosphere models developed at ESOC and their current testing and implementation status.