Helioseismology and standard solar models

We present a systematical analysis of uncertainties in the helioseismological determination of quantities characterizing the solar structure. We discuss the effect of errors on the measured frequencies, the residual solar model dependence and the uncertainties of the inversion method. We find Y_{ph}=0.238-0.259, $R_b/R_\odot=0.708-0.714$ and $\rho_b=(0.185-0.199)$ gr/cm^3 (the index b refers to the bottom of the convective envelope). In the interval $0.2<R/R_\odot<0.65$, the quantity U=P/\rho is determined with and accuracy of $\pm 5$\permille or better. The predictions of a few recent solar model calculations are compared with helioseismological results.