Objective The effects of perilla seed oil (n-3 fatty acids) on bronchial asthma were compared with the effects of corn oil (n-6 fatty acids) in relation to the pulmonary function and the generation of leukotriene B4 (LTB4) and C4 (LTC4) by leucocytes.Methods and Subjects 14 asthmatic subjects were divided randomly into two groups: one group (7 subjects) consumedperilla seed oil-rich supplementation and the other group (7 subjects) consumed corn oil-rich supplementation for 4 weeks. Generation of LTsby leucocytes and respiratory function were comparedbetween the two groups.Results The generation of LTB4 and LTC4 by leucocytes tended to increase in subjects (N=7) with corn oil-rich supplementation, and decrease in subjects (N=7) with perilla seed oil-rich supplementation. Significant differences between the two groups were observed in the generation of LTB4 at 2 weeks (p<0.05) and LTC4 at 2 weeks (p<0.05) after dietary supplementation. Significant increases in the value of PEF (p<0.05), FVC (p<0.01), FEV1 0 (p<0.05) and V25 (p<0.05) were found in subjects who received perilla seed oil supplementation for 4 weeks. And significant differences in the value of FVC (p<0.05) and FEV1 0 (p<0.05) were observed between the two groups after 4 weeks of dietary supplementation.Conclusion These results suggest that perilla seed oilrich supplementation is useful for the treatment of asthma in terms of suppression of LTB4and LTC4generation by leucocytes, and improvement of pulmonary function.