In the series of International Winter Schools on New Developments in Solid State Physics, the fourth one was devoted to the subject: "Two Dimensional Systems: Physics and Devices". For the second time the pro ceedings of one of these Winter Schools appear as a volume in the Springer Series in Solid-State Sciences (the earlier proceedings were published as Vol. 53). The school was held in the castle of MauterndorfjSalzburg (Austria) February 24-28, 1986. These proceedings contain contributions ba:sed on the thirty invited lectures. The school was attended by 179 registered participants (40% students), who came from western European countries, the United States of America, Japan, the People's Republic of China and Poland. As far as the subjects are conterned, several papers deal with the growth and characterization of heterostructures. Dynamical RHEED tech niques are described as a tool for in situ studies of MBE growth mech anisms. Various growth techniques, including MBE, MOMBE, MOCVD and modifications of these, are discussed. The limiting fa.ctors for the carrier mobilities and the inftuence of the spacer thickness in single het erostructures of GaAs/GaAIAs seem to be understood and are no longer a matter of controversy. In addition, the growth of two fascinating systems, Si/SiGe and Hg _ Cd Te/CdTe, is discussed in detail.