N-3 fatty acids, such as fish oil, have been reported to have some beneficial effects in patients with bronchial asthma by suppressing leukocyte function, followed by reduction of the need for pharmacologic agents. To examine the effects of dietary supplementation with perilla seed oil rich in α-linolenic acid (ALA), 23 patients with　asthma took corn oil rich in linoleic acid (LA) for the former two weeks, perilla seed oil for the later two weeks. The asthmatic patients were classified into two groups by the changes of the generation of leukotrienes B4 (LTB4), C4 (LTC4), and B5 (LTB5) during the two courses of dietary modification: one was sensitive to dietary modification, and the other was insensitive to dietary supplementation. We compared the two groups in clinical characteristics. Significant differences were observed in peak flow (PEF), forced expiratory volume in one second (FEV1.0), IgE, sex, obesity index (OI), concentration of serum total cholesterol, albumin, low density lipoprotein {LDL)-cholesterol, β-lipoprotein and phospholipids between two groups. This study indicated that these factors influence the generation of LTB4, C4 and B5 of asthmatic patients in dietary supplementation.