The IUTAM Symposium on Three-dimensional Turbulent Boundary Layers was suggested by the Gesellschaft fur Angewandte Mathe- matik (GAMM) and sponsored by the International Union of theor- etical and Applied Mechanics. The symposium was organized by H.H. Fernholz (Hermann-Fottinger-Institut fur Thermo- und Fluiddynamik der Technischen Universitat Berlin) and E. Krause (Aerodynamisches Institut der RWTH Aachen). After two success- ful Euromech Colloquia on the same topic in Berlin 1972 and Trondheim 1975 the organizers felt that another meeting should be convened, this time with participants from inside and out- side Europe. The aim of the symposium has been to bring together scientists who are actively engaged in boundary layer research, both ex- perimental and theoretical. The scope of the meeting encompass- ed incompressible and compressible three-dimensional turbulent boundary layers. Special emphasis was laid on economical cal- culation methods, on measurements of fluctuating quantities and on measuring techniques designed for and applied success- fully to three-dimensional boundary layers. From among thirty-four papers submitted for presentation, twenty- six contributions of twenty-five minutes each were selected by the European mernbers of the Scientific Committee. Furthermore there were four invited lectures of forty-five minutes. Short discussions were held directly after each presentation with a long discussion period at the end of each day. The final dis- cussion on the last day of the symposium was recorded on tape and is presented in a slightly shortened version as the last contribution in this volume.