Since its initial discovery in the continental USA in 1985, the Asian tiger mosquito, Aedes albopictus, has spread rapidly throughout the eastern part of the country. Infestations of Ae. albopictus now have been reported to the Centers for Disease Control and Prevention from 919 counties in 26 states in the continental USA. This species is believed to be established in 911 counties in 25 states. Single individuals or small numbers of Ae. albopictus have been intercepted and destroyed in 3 additional states (California, New Mexico, and Washington). Five states (Florida, Georgia, North Carolina, South Carolina, and Tennessee) have reported infestations in all of their counties. The current reported distribution of Ae. albopictus was compared to ecoregions of the U.S. Environmental Protection Agency's Level III ecoregion map. Several areas are identified as probable candidates for extension of this species based on ecological characteristics of the landscape. In other areas, populations seem likely to become locally abundant in urban or suburban oases that do not reflect the native ecology of the region. The ability of Ae. albopictus to transmit a variety of pathogens of human and veterinary public health importance, coupled with its ability to colonize diverse ecological settings makes continued surveillance an important issue.