  The elements of a finite nonempty partially ordered set are exposed at
independent uniform times in $[0,1]$ to a selector who, at any given time, can
see the structure of the induced partial order on the exposed elements. The
selector's task is to choose online a maximal element. This generalizes the
classical linear order secretary problem, for which it is known that the
selector can succeed with probability $1/e$ and that this is best possible. We
describe a strategy for the general problem that achieves success probability
$1/e$ for an arbitrary partial order.
