In evaluating fluid cracking catalyst performance in lab-scale testing, selecting the proper catalyst deactivation method is just as important as the testing itself. While the cyclic deactivation (CD) technique of alternately exposing a catalyst to cracking and regeneration cycles using a feed with enhanced metals concentration has been shown to be the most accurate way of mimicking a commercial equilibrium catalyst (e-cat), there have still been difficulties in simulating the catalyst accessibility losses (as measured by the Akzo Accessibility Index (AAI)) associated with iron contamination in the commercial fluid catalytic cracking unit (FCCU). Resistance to the deleterious effects of iron contamination has recently emerged as one of the most critical issues in selecting an appropriate catalyst, particularly in resid applications. The method presented here, a modification of conventional cyclic deactivation, employs lower steam partial pressure and temperature, more consistent with FCCU operation. This results in a more realistic simulation of equilibrium catalyst accessibility responses to iron contamination. (C) 2003 Elsevier Science B.V. All rights reserved.