  We report the results of a phase-referencing study aimed at uncovering
precession of the VLBI jet of BL Lac. The observations were conducted at 8, 15,
22, and 43 GHz and consist of seven epochs spanning about two years. We
investigated the change in the absolute position of BL Lac's radio core by
means of phase-referencing with two nearby sources, 2151+431 and 2207+374. The
shift in the position of the core perpendicular to the jet is a signature of
precession. However, the periodic variations with an amplitude of ~0.15 mas and
a period of 1 year can be attributed to seasonal weather variations. We also
detect a trend in position of the core on the scale of ~0.1 mas over two years.
