Silicon and silicon compounds have contributed decisively to the technical progress. Technical applications range from mass commodities to highly sophisticated special materials, from ceramics to polymers, from medicine to microelectronics. To keep pace with scientific and technical developments Germany and Austria have established national priority programs, strongly linked to each other as well as to some Swiss groups. At mid-term of the German program and the end of the first funding period of the Austrian program the results are summarized in this special edition of the journal Monatshefte für Chemie/Chemical Monthly, giving an excellent overview of the current chemical (and partly physical) acitivites in the joint Austrian/German/Swiss program. The contributions cover topical and interdisciplinary developments in the following areas: • new phenomena in compounds with Si-Si bonds: transitions between molecular compounds and solids, cyclosilanes, polysilanes, silicides, amorphous hydrogenated silicon, • novel silicon-oxygen systems: functionalized sol-gel compounds, spherosiloxanes, siloxene, • compounds with low- and high-coordinated silicon, • new spectroscopic and analytical techniques for the characterization of molecular and polymeric silicon compounds.