Electrolysis at the interface between a Na(AuCl4)-CuSO4 aqueous phase and an immiscible hexyl acetate phase resulted in continuous growth of gold films along the interface. To maintain filmy growth of gold, it was effective to stimulate displacement of predeposited copper with gold by applying a rectangular or triangular potential in a given range. Two types of electrodes were applied : from a point electrode the film grew concentrically like a blooming flower, and from a line electrode the film grew unidirectionally toward the counter electrode as a spreading wave. A long time electrolysis could be performed by circulating and filtering the aqueous solution. The film contained no trace of copper and was very thin (<1 mu m).