  We analyze images of BL Lacertae objects obtained with the {\it Hubble Space
Telescope} WFPC2 and the F814W filter. The nine objects cover a redshift range
of 0.19 to 0.997. The relatively deep images are sufficient to detect galaxies
at least one magnitude below M$^{*}_{I}$ (--21.4) and in most cases to three
magnitudes below M$^{*}$. Galaxy enhancement over the average background is
found around four out of the nine objects. Results for some cases are confirmed
by ground-based imaging. In the other cases, the redshifts of the target BL Lac
objects may be incorrect or they are truly isolated. These findings reinforce
the idea that on average, BL Lac objects are found in regions of above average
galaxy density. However, isolated objects apparently can host BL Lac nuclei
too, a result that has implications for the processes that trigger/fuel the
nuclear activity.
