Red muscardine (P. fumosoroseus), first observed on silkworm in Korea, was examined on its cultural characters, infection process, and symptoms. The fungus on PDA medium was grown to 44 mm in diameter in 14 days. Conidiaphore ws 1.45$mu extrm{m}$ in diameter, producing 4 to 6 phialides (5.9$mu extrm{m}$${ imes}$1.8$mu extrm{m}$) in cluster. Elliptic conidia wre hyaline and 2.9${ imes}$1.3$mu extrm{m}$ in size. Diseased silkworm showed typical symptoms of muscardine while becoming stiff. On 3 to 4 days after inoculation of P. fumosoroseus conidia upon the surface of silkworm, it was observed that the silkworm moved and ate less in rearing bed, and amorpnous dark spots of 1∼2 mm appeared on the surface o thorax, abdomen, spirace, and etc. Corrected mortality reached up to 97% at 9th day after inoculation.