We present the first results of a statistical study of the milliarcsec structure in a complete sample of radio galaxies. We have selected from the B2 and 3CR samples of galaxies the sources which present, at the VLA or WSRT angular resolution, an unresolved core with a flux density at 5 GHz Sc ≥ 100 mJy. The total sample consists of 30 radio galaxies, 17 from the B2 and 13 from the 3CR catalog. This complete sample covers a range of total radio power at 408 MHz log P = 23.5 – 26.5 W/Hz (low-intermediate luminosity). The radio structure of these sources on the arcsec-arcmin scale is well known, thanks to good dynamic range VLA and/or WSRT maps; a large variety of structures is present in the sample, from classical doubles to head-tail sources; flat, inverted and steep spectrum cores are also present.