  We present our results concerning a systematical analysis of helioseismic
implications on solar structure and neutrino production. 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$^3$. 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. At the solar center
still one has remarkable accuracy, $\Delta U/U <4%$. We compare the predictions
of recent solar models (standard and non-standard) with the helioseismic
results. By constructing helioseismically constrained solar models, the central
solar temperature is found to be $T=1.58 \times 10^7$K with a conservatively
estimated accuracy of 1.4%, so that the major unceratainty on neutrino fluxes
is due to nuclear cross section and not to solar inputs.
