  The active galactic nucleus BL Lac was observed with the Gt-48 atmospheric
Cherenkov detector of the Crimean Astrophysical Observatory from July
23-September 1, 1998, in order to search for ultrahigh-energy gamma-ray (>1
TeV) emission. The object was in the field of view of the detector for more
than 24 hours. The source was detected with a high level of confidence (7.2
sigma), with a flux equal to (2.1+/-0.4)x10^{-11} photons cm^{-2}s^{-1}.
