  The effects of random dilution of junctions on a two-dimensional
Josephson-junction array in a magnetic field are considered. For rational
values of the average flux quantum per plaquette $f$, the superconducting
transition temperature vanishes, for increasing dilution, at a critical value
$x_S(f)$, while the vortex ordering remains stable up to $x_{VL}>x_S$, much
below the value $x_p$ corresponding to the geometric percolation threshold. For
$ x_{VL}<x<x_p$, the array behaves as a zero-temperature vortex-glass.
Numerical results for $f=1/2$ from defect energy calculations are presented
which are consistent with this scenario.
