We carried out inoculation tests todetermine whether both sclerotial dieback and Scolicosporium dieback diseases were in fact attributable to the samepathogen. Three kinds of inoculum were prepared : 1. rice bran/mycelium isolated from mycelial strands associatedwith sclerotial dieback ; 2. rice bran/mycelium of a single spore isolate of Scolicosporium sp. from a twig specimenaffected by Scolicosporium dieback ; 3. conidial suspension of Scolicosporium sp. These inocula were separatelytransferred onto the buds of twigs of 5-year-old potted cuttings of Japanese cedar, which had been previously woundedor left unwounded. All three inoculum types resulted in mycelial strands development typical of sclerotial dieback.These results supported that both sclerotial and Scolicosporium dieback diseases were caused by the same pathogen.Futhermore, since the mycelial strands appeared on plant parts which had been inoculated with Scolicosporiumspore-suspension, it was suggested that Scolicosporium sp. might be the infective fungal state which causes sclerotialdieback.