Ballistic measurements were made of the critical magnetic fields of superconducting. cylinders of cerium-doped lead. Within the accuracy of our measurements, the introduction of the paramagnetic impurity, cerium, in lead has no effect other than a slight broadening of the transition. The samples, containing 0.00, 0.10, 1.0, and 1.5 atomic percent cerium in lead had been vacuum cast in pyrex tubes. The relative fractions of the cerium in these samples and their final purities were tested by the techniques of neutron activation analysis. / Master of Science