Hair samples taken from 12-year-old boy prediagnosed with Netherton's syndrome were evaluated by using light and electron microscopic methods. Hair samples were prepared according to routine electron microscopic procedures. Semi-thin sections were stained with methylene blue-azure II, thin sections were contrasted with uranyl acetate-lead citrate. Besides atopy symptoms, hyperparakeratosis and inflammatory cell infiltration were seen in dermis. Results were in accordance with icthyosis linearis circumflexa. In cortex portion of hair, nodulary thickening and swelling were observed. There was a punctured proximal portion like a telescope in distal hair shaft segment. Cells that make up hair cortex were seen to be loosely arranged and there was detachment between cells exterior of cuticle. In evaluating all results trichorrhexis invaginata was identified. Patients given long term therapy for atopic dermatitis, which have breaking of hair in addition to icthyosis, Netherton's syndrome should be thought and investigation of hair samples for supporting the diagnosis is important.