  Let $n$ be a squarefree natural number, and let $G$, $\Gamma$ be two groups
of order $n$. We determine the number of Hopf-Galois structures of type $G$
admitted by a Galois extension of fields with Galois group isomorphic to
$\Gamma$. We give some examples, including a full treatment of the case where
$n$ is the product of three primes.
