Abstract: A report on the electron microscopic observation of the affected hair in three forms of tinea capitis caused by Trichophyton Schoenlein, Trichophyton violaceum and Microsporon ferrugineum is presented. SEM examination showed that: There were the destructions of hair scale, with cavities and fissures is various size and shape, and a mass of oval spores densely crowded together on the surface of the affected hair shaft,Ultrastructural examination that the fungous cells of T. Schoenlein were situated in the medulla and the cortex, thase of T. violaceum is the outer layer of the cortex. However, those of the M. ferrugineum in the cuticle, the latter was different from those observed under light microscopy. Therefore it was suggested that the affected hairs of M. ferrugineum might belong to endo-ectothrix infection.