  Galaxy pairs are ideal sites in which to investigate the role of interaction
on nuclear activity. For this reason we have undertaken a spectroscopic survey
of a large homogeneous sample of galaxy pairs (UZC-BGP) and we present the
results of the nuclear spectral classification of 48 pairs (more than half of
the whole sample). The fraction of emission line galaxies is extremely large,
especially among spirals (84 % and 95 %, for early and late spirals
respectively). SB is the most frequent type of nuclear activity encountered (30
% of galaxies) while AGNs are only 19%. The fractions raise to 45 % and 22 %
when considering only spirals. Late spirals are characterized by both an
unusual increase (35 %) of AGN activity and high luminosity (44 % have M_B
<-20.0 + 5log h). LLAGNs are only 8% of the total number of galaxies, but this
activity could be present in another 10 % of the galaxies (LLAGN candidates).
Absorption line galaxies reside mostly (61 %) in S0 galaxies and display the
lowest B luminosity in the sample, only 18 % of them have M_B < -20 + 5 log h,
but together with LLAGNs they are the most massive galaxies in the sample.
Intense-SB nuclei are found in galaxy pairs with galaxy-galaxy projected
separations up to 160 h^{-1} kpc suggesting that in bright isolated galaxy
pairs interaction may be at work and effective up to that distance. AGNs are
characterized by an advanced morphology while SB phenomenon occurs with the
same frequency in early and late spirals. LLAGNs and LLAGN candidates do not
always show similar properties, a finding which might confirm the heterogeneous
nature of this class of objects. Half LLAGNs are hosted in galaxies showing
visible signs of interaction with fainter companions, suggesting that minor
interactions might be a driving mechanism for a relevant fraction of LLAGNs.
