The class of radio-loud active galactic nuclei (AGNs) called "blazars" includes BL Lacertae objects and quasars presenting a flat radio spectrum, rapid variability, high and variable polarization, high brightness temperature. Their extremely strong emission is probably due to a relativistic beaming effect, because of the small angle between the emitting jet and the line of sight (see e.g. the review paper by Urry & Padovani (1995)).
In order to shed light on the mechanisms that are responsible for the energy
output, astronomers have recognized the importance of performing monitoring
campaigns with a good time coverage and of collecting data simultaneously at
various wavelengths, which often translates into big international
collaborations. Correlations between emissions in different bands are a testing
tool for theoretical models. In particular, the optical flux is expected to be
correlated to the 
one, since relativistic electrons in the magnetized
emitting plasma can produce optical photons by synchrotron and photons
by inverse Compton scattering either on the same synchrotron photons
(synchrotron self-Compton models) or on external soft photons.
Several blazars have now been observed at -ray wavelengths by the
Compton Gamma Ray Observatory (CGRO), which showed how the emission
can in many cases overcome that in the other bands. Moreover, often this
emission was found to be strongly variable
(von Montigny et al. 1995; Lin et al. 1996;
Sreekumar et al. 1996).
With the principal aim of following the optical behaviour of the sources pointed by the Energetic Gamma Ray Experiment Telescope (EGRET) on board CGRO, a program of blazar monitoring was started at the Torino Observatory in November 1994. On some sources collaborations with other groups were set. The results of the first year observations are presented in Villata et al. (1997a), Massaro et al. (1996) about PKS 0422+00, Ghisellini et al. (1997) about S5 0716+71, Tosti et al. (1997a) about PKS 0735+17 and S2 0109+22, Tosti et al. (1997b) about ON 231, Tosti et al. (1997c) and Villata et al. (1997b) about S4 0954+65, Aller et al. (1997) about 3C 454.3; as for OJ 287, 3C 66A, and AO 0235+16, we joined the wide international collaboration named OJ-94 Project (e.g. Sillanpää et al. 1996a,b; Takalo et al. 1996, 1997; Villata et al. 1996).
In this paper we present observations of 22 blazars of our monitoring list from November 1995 to June 1996. Data taken in the same period on S2 0109+22, PKS 0735+17, S4 0954+65, and ON 231 are presented in the aforecited papers, while those on S5 0716+71 and 3C 279 will be published in Wagner et al. (1997) and Pian et al. (1997), respectively. In Sect. 2 (click here) we briefly describe the instruments and data reduction and analysis procedure; light curves are presented in Sect. 3 (click here). Three cases of intranight variations are shown in Sect. 4 (click here). The main conclusions are drawn in Sect. 5 (click here).