A study has been carried out on the cracking of a mixture of atmospheric residue (20 wt %) and VGO (vacuum gas-oil) from a refinery, in a riser simulator reactor under industrial unit conditions in the 525-575 degrees C range, with contact times between 3 and 12 s and using a commercial catalyst for residues. The yields and compositions of the product streams (dry gas, LPG, gasoline, LCO, HCO, and coke) have been compared to those corresponding to a standard feed in a fluidized catalytic cracking (FCC) unit. Catalyst accessibility renders it efficient for maintaining conversion, although overcracking of LCO and gasoline is significant above 550 degrees C, whereas the cracking of the HCO fraction in the residue is significantly limited: The temperature and contact time (especially the former) have a considerable effect on the gasoline composition, because of the significance of overcracking under process conditions. As the temperature is increased, the olefin concentration increases and that of the other fractions in the gasoline decreases, particularly in the case Of C-6-C-9 aromatics.