As a satellite conference to the Fourth Congress of European Mathematics held at StockholmUniversityin2004,theInternationalConferenceonPseudo-Di?erential Operators and Related Topics was held at V.. axjo .. University in Sweden from June 22 to June 25, 2004. The conferencewas supported by Vaxj .. oU .. niversity,theFIRB Research Group on Microlocal Analysis of Universit’ a di Torino, and the Int- national Society for Analysis, its Applications and Computation (ISAAC). The conferencewas well attended by about 50 mathematicians fromBulgaria,Canada, Denmark, England,Finland, Germany,Italy, Japan,Mexico, Serbiaand Monte- gro, Russia and Sweden. The conference covered a broad spectrum of topics related to pseudo-di?erential operators such as partial di?erential equations, quantization, Wigner transforms andWeyltransformsonLiegroups,mathematicalphysics,time-frequencyanalysis and stochastic processes. The speakers were enthusiastic about the prospect of publishing articles based on their presentations in a volume to be published in Professor Israel Gohberg’s prestigious series entitled Operator Theory: Advances and Applications . All contributions from speakers have been carefully refereed and the articles c- lected in this volume give a representative ?avour of the mathematics presented at the conference. This volume is a permanent record of the conference and a valuable complement to the volume Advances in Pseudo-Di?erential Operators published in the same series in 2004, which is devoted to the Special Session on Pseudo-Di?erential Operators at the Fourth ISAAC Congress held at York U- versity in August 2003. Operator Theory: Advances and Applications, Vol. 164, 1-21 c 2006 Birkh. auser Verlag Basel/Switzerland Strongly Elliptic Second Order Systems with Spectral Parameter in Transmission Conditions on a Nonclosed Surface M. S.