Book excerpt: The NATO Advanced Study Institute (ASI) on "Relativistic Effects in Atoms, Molecules and Solids" cosponsored by Simon Fraser University (SFU) and Natural Sciences and Engineering Research Council of Canada (NSERC) was held at the University of British Columbia (UBC) , Van couver, Canada from August 10th until August 21st, 1981. A total of 77 lecturers and students with diverse backgrounds in Chemistry, Physics, Mathematics and various interdisciplinary subjects attended the ASI. In the proposal submitted to NATO for financial support for this ASI, it was suggested that recent impressive experimental developments coupled with the availability of sophisticated computer technology for detailed investigation of the relativistic structure of atoms, molecules and solids would provide an excellent testing ground for the validity and accuracy of the theoretical treatment of the rela tivistic many-electron systems involving medium and heavy atoms. Such systems are also of interest to the current energy crisis because of their usage for photovoltaic devices, nuclear fuels (UF6), fusion lasers (Xe*2)' catalysts for solar energy conversion, etc.