The study of planetary ionospheres and magnetospheres has advanced dramatically in the past two decades, both through careful and increasingly sophisticated analysis of data returned by space probes and through theoretical studies supplemented by extensive computer simulations. The thirty-one papers presented in this volume on planetary ionospheres and magnetospheres include papers on the ionospheres and magnetospheres of Venus, Mars, Jupiter, Pluto and comet Halley. Papers are included that describe observations from many spacecraft missions to the planets and to small solar system bodies. This volume is divided into three sections dealing with: Venus and Mars, the gas giant planets with emphasis on Jupiter and the small bodies in the solar system (Pluto, Io, comets). In the first section the emphasis is on Mars (9 out of 11 papers), providing background relevant to some of the upcoming missions that will target this planet in the closing years of this century. The Mars papers focus on measurements made in the magnetosheath and in the induced magnetosphere of that planet by several instruments onboard the Phobos-2 probe.