  Detailed magneto-transport data on dense wires of $MgB_2$ are reported for
applied magnetic fields up to 18 T. The temperature and field dependencies of
the electrical resistivity are consistent with $MgB_2$ behaving like a simple
metal and following a generalized form of Kohler's rule. In addition, given the
generally high $T_c$ values and narrow resistive transition widths associated
with $MgB_2$ synthesized in this manner, combined with applied magnetic fields
of up to 18 T, an accurate and complete $H_{c2}(T)$ curve could be determined.
This curve agrees well with curves determined from lower field measurements on
sintered pellets and wires of $MgB_2$. $H_{c2}(T)$ is linear in $T$ over a wide
range of temperature (7 K $\le~T~\le$ 32 K) and has an upward curvature for $T$
close to $T_c$. These features are similar to other high $\kappa$, clean limit,
boron-bearing intermetallics: $YNi_2B_2C$ and $LuNi_2B_2C$.
