  We use dispersive techniques to address the behavior of the pion form factor
as $Q^2 \to \infty$ and $Q^2 \to 0$. We perform the matching with the
constraints of perturbative QCD and chiral perturbation theory in the high
energy and low energy limits, leading to four sum rules. We present a version
of the dispersive input which is consistent with the data and with all
theoretical constraints. The results indicate that the asymptotic perturbative
QCD limit is approached relatively slowly, and give a model independent
determination of low energy chiral parameters.
