Whether or not a critical threshold exists when epidemic diseases ' are spread in complex networks is a problem attracting attention from researchers in several disciplines. In 2001. Pastor-Satorras and Vespignani used a computational simulations approach to ' show that epidemic diseases which spread through scale-free ' social networks do not have positive critical thresholds. In other words, even if a disease has almost no chance of being transmitted ' from one person to another, it can still spread throughout a scale-free network. However, they ignored two key factors that have a large impact on epidemic dynamics: economic resource j limitations and transmission costs. Every infection event entails tangible or intangible costs in terms of time, energy, or money to ' the carrier, recipient, or both. Here we apply an agent-based ' modeling and network-oriented computer simulation approach to analyze the influences of resource limitations and transmission ' costs on epidemic dynamics and critical thresholds in scale-free ' networks. Our results indicate that when those resources and costs ' are taken into consideration, the epidemic dynamics of scale-free ; networks are very similar to those of homogeneous networks, including the presence of significant critical thresholds. It is ' hoped that our data will help epidemiologists, public health ' professionals, and computer scientists working with core i questions of epidemic diseases, estimates of epidemic dynamics ; and spreading, and effective public health policies and i immunization strategies.