Previously, I reported that more leukotrienes (LTs) and superoxides were produced from the neutrophil-rich fraction by non-immunological stimulation with CaI in intractable asthmatics than in non-intractable asthmatics. This suggested that neutrophils are involved in the pathogenesis of intractable asthma. To investigate the process of neutrophil activation in intractable asthma, the LTs production from neutrophils by immunological stimulation was measured by high performance liquid chromatography (HPLC). LTs were produced from neutrophils by stimulation of anti-IgG and zymosan activated serum (ZAS), but not anti-IgE. However, there was no significant difference with each disease severity of asthma. The production from neutrophils was also detected by Candida antigen stimulation. Moreover, the production of LTC4 from neutrophils by this stimulation was higher in intractable asthmatics than in non-intractable asthmatics. These findings suggested that neutrophils are produced LTs by immunological stimulation such as by Candida antigen based on the IgG mediated allergy reaction, and play an important role in the pathogenesis of intractable asthma.