The Japanese beetle, Popillia japonica, is a damaging plant pest introduced from Japan into New Jersey in 1916. It has since spread and established in most states east of the Mississippi River. Several partially established areas and infestations occur west of the Mississippi River, including Montana. First found in Montana in 1998 at Logan International Airport in Billings, a small population has become established in a four-block area surrounding the MSU-Billings Campus. Adult beetles have been found at 17 plant nurseries throught the state of Montana. It remains to be seen whether the Japanese beetle will become established because of these introductions. This MontGuide will provide guidance for monitoring, detecting and controlling the beetle. Downloadabe in color, 8 pages.