  We characterize the postulation character of arithmetically Gorenstein curves
in ${\mathbb P}^4$. We give conditions under which the curve can be realized in
the form $mH-K$ on some ACM surface. Finally, we strengthen a theorem of
Watanabe by showing that any general arithmetically Gorenstein curve in
${\mathbb P}^4$ can be obtained from a line by a series of ascending
complete-intersection biliaisons.
