During studies of bat populations of about 100 caves in the Kentucky area, a hibernating colony of about 100,000 gray bats, Myotis grisescens, was found in a cave in Edmonson County, Kentucky. Summer colonies were found in 10 caves in Kentucky, Illionois, and Tennessee. Of 3,072 gray bats banded in the winter colony only 12 were recovered in the summer, with one movement of 102 miles. Of 1,622 banded in 6 summer colonies in Kentucky and Illinois, 153, or 9.4% were recovered in the hibernating colony in Edmonson County, Kentucky. These various summer colonies from which bats moved to the one hibernating colony are scattered over an area of about 10,500 square miles of Kentucky, southern Illinois, and northern Tennessee.