Statistics on thc incidence of damaging lighting in Illinois during the 1914–47 period were gleaned largely from published and unpublished records of the U.S. Weather Bureau to perform a climatological investigation. On the average, damaging lightning was most frequent during July and August. Normally, 14 days per year had damaging lightning, and during the 1926–47 period lightning was responsible for more deaths than any other form of severe weather. Other forms of severe weather occurred on less than 50 percent of the days of damaging lightning. On an areal basis, damaging lightning occurred most frequently in west-southwestern Illinois which is the same area that has been found to have a high incidence of thunderstorms, tornadoes, hailstorms, and excessive rainstorms. Lightning caused deaths and injuries to a greater percentage of the rural population than of the urban population of the State. In rural areas the structures most frequently damaged by lighnting were farm barns, whereas in urban areas residences were the structures most frequently damaged.