The agglomerate model of a polymer electrolyte fuel cell (PEFC) electrode typically assumes a single, representative agglomerate diameter, while in reality there is a distribution of agglomerate sizes. Here, we analyze how the agglomerate model's predictions are affected by incorporating an agglomerate diameter distribution. Our analysis shows that the diameter distribution causes the agglomerate model predictions to differ by as much as 70% when compared to even reasonable single agglomerate diameter choices. The error in the model's predictions is highly sensitive to both agglomerate diameter and overpotential. Even the agglomerate diameter that gives the lowest maximum error in our results, 115 nm, errs by as much as 15% at certain overpotentials. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.