To handle the uncertainty inherent in eCommerce transactions, reputation systems have emerged as a way to represent reliability and develop trust between transaction participants. Despite the value added by reputation systems, limitations of existent systems remain (Malaga 2001). We empirically test Porter et al.’s (2004) reputation scoring procedure, which was designed to address the shortcomings of current systems. This study uses computer simulation to replicate the auction process between buyers and sellers with reputation scores calculated using both the Porter et al. model and the eBay auction model. Results from the two models are then analyzed to show that the Porter et al. model more accurately estimates reputation scores.