  The results of medium-band photometry of 1037 stars in the area of old open
cluster NGC 7142 down to V = 20.1 mag in the Vilnius seven-colour system are
presented. Photometric results are used to classify in spectral and luminosity
classes about 80 percent of stars down to V = 18.5 mag, to identify cluster
members, to determine the main cluster parameters and to investigate the
interstellar extinction in this direction. The average extinction A_V of the
cluster is about 1.1 mag, E(B-V) = 0.35, and its distance is 2.3 kpc (the
distance modulus 11.8 mag). The age of the cluster, 3.0 Gyr, is estimated from
the intrinsic colour-magnitude diagram with individual dereddening of each star
and the Padova isochrones. The surface distribution of the extinction is shown.
The reddening of the eclipsing variable V375 Cep is found to be close to the
average reddening of the cluster. Probably, the cluster contains five red clump
giants, two asymptotic branch stars and four blue stragglers.
