During 2003–2006, a general aphid survey was conducted in the Great Smoky Mountains National Park in the American states of Tennessee and North Carolina. The project was undertaken within the context of the All Taxa Biodiversity Inventory and funded by Discover Life in America. In all, 121 aphid species were documented. When present, attendant ants were also collected and identified, as were the aphid host plants. The aphids, their attendant ants, and host plants are listed here. In addition, a checklist of the plants of the park and a catalog of the aphids of North America were cross-referenced to create a list of aphids not actually found but likely present in the Great Smoky Mountains National Park, increasing the number to 206. Finally, we used Chao1 statistical techniques to estimate the total number of aphid species based on our sampling to date. These produced estimates of 201–214 species.