Dynamic nuclear polarization experiments have been carried out on proton resonances at 53.2 Mc/s with the use of a magnetic field of 12500 G and 8 mm microwave radiation. The nuclear polarization at infinite microwave power is equal to that expected for the extreme narrowing case, using measured values of the nuclear spin-lattice relaxation times. The rate at which the nuclear polarization is built up during the experiment is equal to the rate at which it decays due to spin-lattice relaxation. When the enhancements for infinite power are extrapolated to infinite radical concentration, the ratio of the signal strength before and after enhancement is close to -330 as expected for dipole coupling. For mobile organic liquids the case of extreme narrowing does seem to be reasonably applicable.