This proceedings volume is a collection of papers presented at the International Conference on SPT2004 focusing on symmetry, perturbation theory, and integrability.The book provides an updated overview of the recent developments in the various different fields of nonlinear dynamics, covering both theory and applications. Special emphasis is given to algebraic and geometric integrability, solutions to the N-body problem of the “choreography” type, geometry and symmetry of dynamical systems, integrable evolution equations, various different perturbation theories, and bifurcation analysis.The contributors to this volume include some of the leading scientists in the field, among them: I Anderson, D Bambusi, S Benenti, S Bolotin, M Fels, W Y Hsiang, V Matveev, A V Mikhailov, P J Olver, G Pucacco, G Sartori, M A Teixeira, S Terracini, F Verhulst and I Yehorchenko.Contents:Parametric Excitation in Nonlinear Dynamics (T Bakri)Similarity Reductions of an Optical Model (M S Bruzón & M L Gandarias)A Regularity Theory for Optimal Partition Problems (M Conti et al.)Periodic Solutions for Zero Mass Nonlinear Wave Equations (G Gentile)Renormalization Group Symmetry and Gas Dynamics (S Murata)Refined Computation of Hypernormal Forms (J Murdock)Regularity of Pseudogroup Orbits (P J Olver & J Pohjanpelto)On Birkhoff Method for Integrable Lagrangian Systems (G Pucacco)and other papersReadership: Researchers and academics.