The role of the dispersed oil phase in thermal conduction was examined for thick oil-in-water emulsions prepared with corn oil as the oil phase and egg yolk as the emulsifier. The rate of temperature increase of an emulsion heated at 105°C was detected one-dimensionally along an axis 0-10 mm from the heating plane at the bottom of the vessel. An optical microscopic examination of each tested emulsion suggested a negatively skewed distribution with the most frequent globules of 1.5-2.0 μm in diameter for the dispersed oil phase. Each emulsion could be characterized by a pseudo plastic body. The apparent viscosity and Casson's yield value increased with increasing volume fraction of the dispersed phase. The retardation time for the thermal conduction at each location also increased with increasing volume fraction of the dispersed oil globules, while the thermal diffusivity of each emulsion tended to decrease with increasing volume fraction of the oil phase.