  In this paper, we characterise the family of finite arc-transitive
bicirculants. We show that every finite arc-transitive bicirculant is a normal
$r$-cover of an arc-transitive graph that lies in one of eight infinite
families or is one of seven sporadic arc-transitive graphs. Moreover, each of
these "basic" graphs is either an arc-transitive bicirculant or an
arc-transitive circulant, and each graph in the latter case has an
arc-transitive bicirculant normal $r$-cover for some integer $r$.
