  We present a straightforward method for particle identification and
background rejection in $^3$He proportional counters for use in neutron
detection. By measuring the risetime and pulse height of the preamplifier
signals, one may define a region in the risetime versus pulse height space
where the events are predominately from neutron interactions. For six
proportional counters surveyed in a low-background environment, we demonstrate
the ability to reject alpha-particle events with an efficiency of 99%. By
applying the same method, we also show an effective rejection of microdischarge
noise events that, when passed through a shaping amplifier, are
indistinguishable from physical events in the counters. The primary application
of this method is in measurements where the signal-to-background for counting
neutrons is very low, such as in underground laboratories.
