This text book is intended for studies in wind engineering, with focus on the stochastic theory of wind induced dynamic response calculations for slender bridges or other line ?like civil engineering type of structures. It contains the background assumptions and hypothesis as well as the development of the computational theory that is necessary for the prediction of wind induced fluctuating displacements and cross sectional forces. The simple cases of static and quasi-static structural response calculations are for the sake of completeness also included. The text is at an advanced level in the sense that it requires a fairly comprehensive knowledge of basic structural dynamics, particularly of solution procedures in a modal format. None of the theory related to the determination of eigen ?values and the corresponding eigen ?modes are included in this book, i. e. it is taken for granted that the reader is familiar with this part of the theory of structural dynamics. Otherwise, the reader will find the necessary subjects covered by e. g. Clough & Penzien [2] and Meirovitch [3]. It is also advantageous that the reader has some knowledge of the theory of statistical properties of stationary time series. However, while the theory of structural dynamics is covered in a good number of text books, the theory of time series is not, and therefore, the book contains most of the necessary treatment of stationary time series (chapter 2). The book does not cover special subjects such as rain-wind induced cable vibrations.