We present a quantitative estimate of the accuracy of the calculated
diffusion coefficients, by comparing predictions of solar models with
observational data provided by helioseismology. By taking into account the
major uncertainties in building solar models we conclude that helioseismology
confirms the diffusion efficiency adopted in SSM calculations, to the 10%
level.Comment: 5 pages with 1 ps figure included, LaTeX file with l-aa.sty,
submitted to Astronomy and Astrophysic
