The long-capillary method was used to measure chemical diffusion in molten AlNiCe alloys. The interdiffusion coefficients were determined for a mean concentration of Al(87)Ni(10)Ce(3) at 1273 K and for a mean concentration of Al(77)Ni(20)Ce(3) at 1373 K. The absence of major convection disturbances and of macro-segregation was demonstrated by time-dependent diffusion measurements. An in-situ x-ray monitoring technique for real-time concentration profile determination is presented.