Gaseous isotopes may be separated by enhanced diffusion in oscillatory flow. This paper evaluates the application of this method to the enrichment of deuterium. The oscillations of the carrier raise the diffusional flux without changing the diffusional character of the transport. The process has been well studied and is derived from primary principles. It follows Fick’s law. Experimental work shows excellent agreement with the theory. The maximal increase of diffusional flux of H-2(2) in water vapor as the carrier by the oscillations reaches 1200 times. The process is tuned for optimal separation from H-2(1). Some modifications of the standard diffusion setup were introduced : The separation ratio was raised 50 times by having the diffusion take place against a low velocity, constant, upstream current of the carrier; the yield was raised 60-fold by concentrating the feed within the reservoir at the high concentration end of the diffusing path. These combined modifications improve the cost effectiveness of the system by several orders. The method may be further improved. It is versatile in that the yield and the separation ratio can be freely chosen over a large range by adjusting the operating conditions.