AbstractIn this paper we discuss two methods to achieve high nuclear polarizations at room temperature using pulsed EPR techniques and triplet spins which are optically excited by a laser pulse. The results of our experiments, which are performed on a single crystal of napthalene doped with pentacene, show that an unusually high proton spin polarization can be achieved and that the transfer occurs in a time determined by the dipolar interaction between the electron spins of the pentacene guests and the proton spins on the surrounding napthalene molecules.