This book presents the "helical wormlike chain" model – a general model for both flexible and semiflexible polymer chains. It explains how statistical-mechanical, hydrodynamic, and dynamic theories of their solution properties can be developed on the basis of this model. This new second edition has been carefully updated and thoroughly revised. It includes a new chapter covering "Simulation and More on Excluded-Volume Effects", as well as the discussion of new experimental data and the application of the theory to ring polymers. The authors provide analysis of important recent experimental data by the use of their theories for flexible polymers over a wide range of molecular weights, including the oligomer region, and for semiflexible polymers, including biological macromolecules such as DNA. This is all clearly illustrated using a reasonable number of theoretical equations, tables, figures, and computer-aided forms, which support the understanding of the basic theory and help to facilitate its application to experimental data for the polymer molecular characterization.