Several aspects of the insulator-metal transition below the magnetic-ordering temperature in EuO have been examined. The conductivity above 50 K is shown to be thermally activated, with an activation energy which depends linearly on the long-range magnetic order. Below 50 K the conductivity is metallic. This insulator-metal transition is observed only in samples which are slightly oxygen deficient, presumably in the form of vacancies. The magnitude of the exchange interaction between the conduction electron and localized spins is shown to be about 0.1 eV. © 1972 The American Physical Society.