The result of a collaboration between a theoretician and an experimentalist, this book is devoted to the static properties of flexible polymers in solution. It presents the vast progress made by both theory and experiment in recent years. Despite the variety in the chemical composition and physical properties of long polymer chains, when in solution they show a universality in their behaviour. On the experimental side, the use of photon and neutron scattering has led to a better understanding, while the use of computer simulation has also produced interesting results. This work is the result of a collaboration between a theoretician and an experimentalist, who have both worked for many years on polymer solutions.