  We present analysis of Hubble Space Telescope images of 82 nearby field
late-M and L dwarfs. We resolve 13 of these systems into double M/L dwarf
systems and identify an additional possible binary. Combined with previous
observations of 20 L dwarfs, we derive an observed binary fraction for
ultracool dwarfs of 17+4-3%, where the statistics included systems with
separations in the range 1.6-16 A.U. We argue that accounting for biases and
incompleteness leads to an estimated binary fraction 15+-5% in the range 1.6-16
A.U. No systems wider than 16 A.U. are seen, implying that the wide companion
frequency is less than 1.7%; the distribution of orbital separation is peaked
at ~2-4 A.U. and differs greatly from the G dwarf binary distribution. Indirect
evidence suggests that the binary fraction is ~5+-3% for separations less than
1.6 A.U. We find no evidence for differences in the binary fraction between
stellar late-M and L dwarfs and substellar L dwarfs. We note, however, that the
widest (>10 A.U.) systems in our sample are all of earlier (M8-L0) spectral
type; a larger sample is needed determine if this is a real effect. One system
with a spectral type of L7 has a secondary that is fainter in the HST F814W
filter but brighter in F1042M; we argue that this secondary is an early-T
dwarf.
