Conjugated polymers are attractive from the viewpoint of possible applications as novel nonlinear optical materials and conductive materials. They are also very important as a group of materials of one dimensionality. The progress of research in this field is very rapid. At the present stage it is extremely useful to have review articles giving information on the most recent progress.Relaxation in Polymers contains state-of-the-art reviews on: ultrafast responses in various conjugated polymers with large optical nonlinearity; ultrafast relaxation in polysilanes; electronic properties of polysilanes; fast transient photoconductivity studies of polyacetylene and polydiacetylene; evolution of photoexcitations in polyacetylene and related polymers from femtoseconds to milliseconds; photoexcited states in conjugated polymers, optical properties of halogen-bridged mixed-valent metal complexes and dynamics of soliton pairs in polyacetylene.