Adsorption isotherms for pure bitumen/aqueous solution of the non-ionic surfactant Intan-100 have been determined as a function of temperature using enhanced video pendant drop technique. The area/molecule occupied by the surfactant at the bitumen/water interface is about 3 times higher at 30 degrees C than at 60 degrees C at which maximum packing occurs. Isotherms for the model system heptane/aqueous solutions of Intan-100 indicate that maximum packing is not possible in the temperature range 20-60 degrees C. This fact implies that bitumen/water interface is a unique system where the natural surfactant present in the bitumen is playing a competitive role at the interface.