A fluid catalytic cracking (FCC) study of 10 vacuum gas oil feeds was performed using a fixed-bed microactivity test (MAT) unit. Gas, liquid, and coke yields at several conversion levels were compared with reported pilot plant data obtained from a modified ARCO riser reactor using the same feeds. The data indicated that except for coke yield, MAT results were, in most cases, within 15% of the corresponding riser yields. Good linear correlations could be established between MAT and riser yields except for liquefied petroleum gas (LPG) and light cycle oil (LCO). Causes for the relatively poor correlations for the two products were analyzed and discussed. Despite the substantial differences in reactor design, flow pattern, and operation between the two systems, the MAT unit can predict the riser performance when appropriate test conditions are applied.