We present M-theory compactifications on K-3 x K-3 with membranes near
the A(n) or D-n singularities of the K-3 spaces, By realizing each of
these compactifications in two different ways as type I' models with
2- and 6-branes, we explain the three-dimensional duality between gaug
e theories recently found by Intriligator and Seiberg. We also find ne
w pairs of dual gauge theories, which we briefly describe. (C) 1997 El
sevier Science B.V.