To describe the behavior of the molten core in the case of a loss-of-coolant accident with core melting, data on the properties of such core melts are required. These properties are dependent on the composition and structure of the melts. Available experimental evidence was used to define four types of melts that would occur, depending on the oxidation potential of the environment. Theoretical and experimental results were reviewed with a view to estimating such properties as heat capacity, viscosity, and thermal conductivity.