The incessant development of quantum chemistry since the appearance of the Schrodinger ¨ equation has turned this area into a respectable branch of science with unprecedented capabilities. It is now a well-recognized eld of research with pred- tive power that is an important component in physical–chemical laboratories. Very important developments were conducted in the early days by bright theoretical s- entists that were ready to absorb the incredible and unpredicted computer revolution which was only just beginning. Isolated medium-size molecular systems can now be accurately studied theoretically by quantum chemical methods. However, it was also long recognized that all biomolecular phenomena necessary to obtain and sustain living systems take place in solution, as well as the vast majority of chemical p- cesses. Indeed solvent and liquid systems are germane in chemistry experiments. In physics, aconstant concern isthedescription of theroleplayed by theenvironment in modifying the properties of the system as compared to the isolated situation. Hence, the importance of studying atoms, molecules and biomolecules in the solvent en- ronment can hardly be denied. The quantum chemical studies of molecular systems affected by the interaction with a solvent had its own turning point before the end of the 1970s, when some pioneering work was done, including the dielectric pr- erties of the medium in an effective nonlinear Hamiltonian. This naturally led to the development of the so-called continuum models that are important and now popular. Continuum models can be implemented from the simplest to the most sophisticated quantum chemical methods.

Prof. Sylvio Canuto (editor of this review volume) is a professor of physics at University of Sao Paulo and is presently serving as: A member of the advisory editorial board of the Chemical Physics Letters (Elsevier); a member of the editorial board of the International Journal of Quantum Chemistry (John Wiley); a specialist editor of the Computer Physics Communications (North Holland); an associate editor of the Brazilian Journal of Physics; a member of the editorial board of the Journal of Computational Methods in Science and Engineering; a member of the International Scientific Advisory Board of the Journal of the Argentine Chemical Society. In addition to these duties, he is co-editor of the following SI volumes: an International Journal of Quantum Chemistry, 106 (2006) issue no. 13; an International Journal of Quantum Chemistry, 103 (2005) issue no. 5.; the Journal of Molecular Structure (Theochem), 464 (1999) issue 1-3.; the Brazilian Journal of Physics, 34 (2004) issue 1.; and the Brazilian Journal of Physics, 24 (1994) (part of) issue 4.

Prof. Canuto has co-edited the following books: Electronic Structure of Atoms, Molecules and Solids. Proceedings of the 2^nd Brazilian School on Electronic Structure. J. DÁ. Castro, S. Canuto and F. Paixao. World Scientific, 1990.; and I Escola Brasileira de Estrutura Eletrônica, Ed. Universidade de Brasília (1989), 587 pages (in portuguese) and co-authored: Teoria Quântica de Moléculas e Sólidos, ed. Livraria da Física, (2004), 400 pages (in portuguese) J D M Vianna, A. Fazzio and S. Canuto.