Recently, we have also reported that spa therapy combined with dietary supplementation of perilla seed oil would be effective for patients, and would suppress the generation of leukotriene C4 (LTC4) by peripheral leucocytes. However, it is still unclear how the combination spa therapy and dietary supplementation of perilla seed oil influences on the pathophysiology of bronchial asthma. In the present study, the effects of spa therapy combined with dietary supplementation of perilla seed oil were examined in patients with asthma in relation to the serum eosinophil cationic protein (ECP) levels to investigate the effect on bronchial asthma. Ten adult asthmatic patients with moderate type asthma in terms of severity were taken to have a complex spa therapy and consume perilla seed oil-rich diet for 4 weeks. The generation of LTC4 by peripheral leucocytes, serum ECP level and pulmonary function were measured. Significant decreases were observed for LTC4 and ECP for 4 weeks. Forced vital capacity (FVC), which was one of the pulmonary function tests, improved significantly at 4 weeks (p<0.05). The number of eosinophils decreased for 4 weeks, but the differences were not significant. The results obtained here suggest that spa therapy combined with dietary supplementation of perilla seed oil leads to decrease in LTC4 and ECP and improves pulmonary function and asthma control.