Abstract. In this paper we construct a global, continuous flow of solutions to the Camassa-Holm equation on the entire space H 1 . Our solutions are conservative, in the sense that the total energy (u 2 + u 2 x ) dx remains a.e. constant in time. Our new approach is based on a distance functional J(u, v), defined in terms of an optimal transportation problem, which satisfies d dt J(u(t), v(t)) ≤ κ · J(u(t), v(t)) for every couple of solutions. Using this new distance functional, we can construct arbitrary solutions as the uniform limit of multi-peakon solutions, and prove a general uniqueness result.