The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an exotic insect new to North America. Large numbers of adult BMSB were first identified in fall 2001 in Allentown, PA; however, undetermined sightings likely date as far back as 1996. This Asian native, sometimes called the yellow-brown or East Asian stink bug, has since been found in several Pennsylvania counties, in New Jersey on plant material and in blacklight traps, and in western Maryland on buildings in 2003. In 2004, BMSB also was detected in West Virginia. The list of positive states will continue to expand as awareness increases.