In July 2001, rotting and shivering flowers of cotton rose (Hibiscus mutabilis) were found in the flower beds along the roadsides in Jinju area. The disease first started as water-soaking, dark-green lesions on the petals, and then whole flower was rotted rapidly. Whitish mycelia and monosporous sporangiophore with monosporous sporangiola were formed abundantly on the lesions. Colony apperared as white to pale yellowish brown mycelia on potato dextrose agar medium (PDA). Monosporous sporangiophore was long slender and branched at the apex, each branch bearing a head of sporangiospores. Sporangium was subglobose in shape and was 42.6~114.2 mm in size. Monosporous sporangiola were elliptic, fusiform or ovoid, and brown in color and 12.3~21.6×8.3~11.6 mm in size. Sporangiospores were elliptic, fusiform or ovoid in shape, dark brown or brown in color and 16.3~23.8×8.2~13.6 mm in size, and they had three or more appendages at bipolar end. Zygospores were mostly globose, dark black colored and sized was 42.6~78.4 mm in diameter. The fungus grew on PDA between at 15 to 40oC, and the optimum temperature was 30oC. This is the first report on the flower rot of cotton rose caused by C. cucurbitarum in Korea.