Coronal mass ejections are the most dynamic phenomena in our solar system. They abruptly disrupt the continuous outflow of solar wind by expelling huge clouds of magnetized plasma into interplanetary space with velocities enabling to cross the Sun-Earth distance within a few days. Earth-directed CMEs may cause severe geomagnetic storms when their embedded magnetic fields and the shocks ahead compress and reconnect with the Earth‘s magnetic field. The transit times and impacts in detail depend on the initial CME velocity, size, and mass, as well as on the conditions and coupling processes with the ambient solar wind flow in interplanetary space. This session is dedicated to derive more insight into the physical processes that CMEs encounter when propagating from Sun to Earth and beyond. Due to the wealth of observational data from multiple viewpoints, over a wide range of wavelengths, and over large distance ranges, as well as recent progress in simulations, we may adequately address this issue. We focus on studies covering observations as well as simulations from which parameters might be gained, essential to better understand the propagation behavior of CMEs in interplanetary space.