This volume deals with the instability of fluid flows that vary spatially in the streamwise direction. Such flows occur widely in nature and industry, but unlike their parallel flow counterparts have hitherto received little attention. The individual chapters in this book were selected from papers presented at the IUTAM Symposium on Nonlinear Instability of Nonparallel Flows, held in Postdam, New York, in 1993, and provide an extensive insight into the state of research in this area. Particular emphasis is given to analytical techniques and their use to interpret numerical and experimental results.