Let $M$ be a smooth 4-manifold which admits a relatively minimal
hyperelliptic genus $h$ Lefschetz fibration over $S^2$. If all of the
vanishing cycles for this fibration are nonseparating curves, then we
show that $M$ is a 2-fold cover of an $S^2$-bundle over $S^2$, branched
over an embedded surface. If the collection of vanishing cycles for this
fibration includes $\s$ separating curves, we show that $M$ is
the relative minimalization of a Lefschetz fibration constructed as a
2-fold branched cover of $\cp \# (2\s+1) \cpb,$
branched over an embedded surface.