SUMMARYOne hundred and six patients with chronic dermatophytosis unresponsive to griseofulvin were studied.Trichophyton rubrumwas the causative organism in 93% of cases. Chronic dermatophyte infections caused by organisms other thanT. rubrumoccurred predominantly, but not exclusively, in patients with underlying diseases. Forty‐nine percent of the patients had a personal or family history of atopy but other abnormalities included disorders of keratinization, collagen vascular disease and systemic steroid therapy. The commonest sites of infection were the palms and soles, as opposed to toe webs or groins in control patients with griseofulvin‐res‐ponsive dermatophyte infections. A significant proportion of chronically infected patients had raised IgE levels. Only 11% of the chronically infected group showed delayed hypersensitivity responses to intradermal trichophytin but 58% showed immediate hypersensitivity responses to trichophytin as well as other fungal and non‐fungal al