Asteroseismology may help detect diffusion-induced helium gradients inside Main-Sequence A stars. Models have been computed for 1.6 and 2.0 $M_{\odot}$ stars with pure helium diffusion, at different ages, so that the helium gradient lies at different depths inside the star. The adiabatic oscillation frequencies have been analysed and compared with those of a model without diffusion. Clear signatures of the diffusion-induced helium gradient are found in the so-called “second differences”. These frequency differences present modulations due to the partial reflection of the sound waves in the layer where the helium gradient occurs. A tentative application to the roAp star HD 60435 is presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html