Book excerpt: Paperback. The Heliosphere is the large volume of space dominated by the expanding solar atmosphere. Even the most distant spacecraft, now at more than sixty Astronomical Units (1 Astronomical Unit = 150 million kilometers) from the sun, have yet to encounter the boundary between the Heliosphere and interstellar space. This publication contains 30 papers, reporting observations made throughout the Heliosphere and presenting theories to explain these observations. The results of the Ulysses spacecraft mission, the first to explore the Heliosphere over the solar poles, are summarised. Modulation of the galactic cosmic radiation and energetic solar particles by heliospheric structures is discussed. New results on the anomalous component of cosmic radiation are given, and predictions are made as to where the boundary of the Heliosphere may be found.