A sclerotinia rot of Leonurus sibiricus caused by Sclerotinia sclerotio겨m occurred severely in farmer`s fields at Seosang-myon, Hamyang-gun, Gyeongnam Province, Korea in 2001. The typical symptoms of the disease were that leaves, stems or collar of the infected plants at first became darker green and then watery soft rotted, and white fluffy mycelia formed on the lesion developed into black sclerotia later, Sclerotia on the plant and PDA medium were globose to cylindrical or irregular in shape, and 0.8~10.30.8~6.4 m in size. Aphothecia with numerous asci were cup-shape, and 0.6~1.2 cm in diameter, Asci with 8 spores were cylindrical, and 87~2464.6~21.6 in size. Ascospores of one cell were hyaline, ellipsoid to ovoid in shape, and 10.2~14.64.7~7.2 in size. The range of temperature for mycelial growth was from 5 to 3, and the optimum was . This is the first report on the sclerotinia rot of L. sibiricus caused by Sclerotinia sclerotioum in Korea.