These proceedings are based upon introductory talks, research reports and discussions from the NATO Advanced Workshop on the "Morphology and Dynamics of the Polar Cusp", held at Lillehammer, Norway, 7-12 May, 1984. The upper atmosphere at high latitudes is called the "Earth's win­ dow to outer space". Through various electrodynamic coupling process­ es as well as through direct transfer of particles many geophysical effects displayed there are direct manifestations of phenomena occurring in the deep space. The high latitude ionosphere will also exert a feedback on the regions of the magnetosphere and atmosphere to which it is coupled, acting as a momentum and energy source and sink, and a source of particles. Of particular interest are the sections of the near space known as the Polar Cusp. A vast portion of the earth's magnetic field envelope is electrically connected to these regions. This geometry results in a spatial mapping of the magnetospheric pro­ cesses and a focusing on to the ionosphere. In the Polar Cusps the solar wind plasma has also direct access to the upper atmosphere. The polar regions are thus of extreme importance when it comes to under­ standing the physical processes in the near space and their effect on our environment. The Introductory Talks given at this workshop provided a common background for discussing and understanding the physics of the Polar Cusp. By this book we will make the information which thus was provid­ ed to the participants of the workshop accessible to a wider audience.