The paper presents the results of BVRI CCD photometry of the radio galaxies 3C 31, 3C 66B, and 3C 120, and V polarimetry of 3C 120. The photometry of the jet of 3C 66B definitively establishes the synchrotron nature of the optical emission. No optical counterpart of the radio counterjet in 3C 66B and of the radio jets in 3C 31 and 3C 120 is found. A rotating ring and an ionized region are present, respectively, in 3C 31 (NGC 383) and its companion galaxy NGC 382, but no isophotal distortions are found which could have revealed a gravitational interaction between the two galaxies as is the case in 3C 66B. The elliptical isophotes of 3C 120 show a slight off-centering, roughly in the direction of the radio jet, very much like 3C 66B. An upper limit of 20 percent is found for the polarization level of the condensations in 3C 120. 50 refs.