The antifungal activity of N-chlorotaurine (NCT), a long-lived oxidant produced by stimulated human leucocytes, was investigated. Incubation of Aspergillus spp., Candida spp., Fusarium spp., Penicillium spp. and Alternaria spp. in 1% NCT (55 mM) for 1-4 h produced a log10 reduction in cfu of between 1 and 4. In samples of nasal secretion, killing was significantly hastened (30 min), which may be explained by the formation of monochloramine by halogenation of ammonium, which was found at a concentration of 1 mM in these samples. For these reasons, NCT is of interest as a new agent for treatment of local inflammatory mycosis, e.g. eosinophilic fungal rhinosinusitis.