  Green's function Monte Carlo calculations of magnetic moments and M1
transitions including two-body meson-exchange current (MEC) contributions are
reported for A<=7 nuclei. The realistic Argonne v18 two-nucleon and Illinois-2
three-nucleon potentials are used to generate the nuclear wave functions. The
two-body meson-exchange operators are constructed to satisfy the continuity
equation with the Argonne v18 potential. The MEC contributions increase the
A=3,7 isovector magnetic moments by 16% and the A=6,7 M1 transition rates by
17--34%, bringing them into very good agreement with the experimental data.
