For many random walks on "sufficiently large" finite
groups the so-called cut-off phenomenon occurs: roughly stated, there
exists a number $k_0$ , depending on the size of the group, such that $k_0$
steps are necessary and sufficient for the random walk to closely approximate
uniformity. As a first example on a continuous group, Rosenthal recently proved
the occurrence of this cut-off phenomenon for a specific random walk on
$SO(N)$. Here we present and [for the case of $O(N)$] prove results for random
walks on $O(N), U(N)$ and $Sp(N)$, where the one-step distribution is a
suitable probability measure concentrated on reflections. In all three cases
the cut-off phenomenon occurs at $k_0 = 1/2 N\log N$.