We have previously reported morphological changes ofTrichophyton violaceum andMicrosporum canis in hair apparatuses in tinea capitis. To investigate the morphology ofTrichophyton rubrum in the human hair apparatus, two cases of tinea capitis and one case of tinea barbae were examined by light- and electron microscopy. The fungal elements, which were located in the lower keratogenous zone, showed non-septate hyphae in the outer part of the hair cortex. With the upward development of the hair layers, some hyphae invaded the keratinized hair cuticle and keratinized inner root sheath and were transformed into arthrospores. Some hyphae remaining in the hair cortex were also transformed into arthrospores, while other hyphae in the hair cortex did not survive, but degenerated. InT. rubrum hair infection, there is a distinct relationship between the morphological changes of the fungi and the hair cell differentiation as seen inT. violaceum andM. canis infections. However,T. rubrum displays unique morphological changes, which are different from those ofT. violaceum andM. canis, in hair apparatuses.