When molecular diffusion through a viscous surface boundary layer is the limiting factor in interfacial gas exchange, theory and experiment show that the periodic surface dilation produced by capillary ripples will decrease the average thickness of the boundary layer and increase gas transfer. This increase is independent of boundary layer thinning by turbulence. For surface dilations typical of the sea surface with fully developed capillary ripples, theCO2transfer may be 3.5 times the flat‐surface value.