We examined the clinical effects of the administration of Saiboku-to (TJ-96 7.5g/day) on 14 patients suffering from chronic bronchial asthma. The observation period was from 22 to 52 weeks, and the administration period 26 to 52 weeks. Eight out of 14 cases (57.1%) showed slight improvement or better with respect to asthmatic points and clinical phenomenon. A Steroid-sparing effect was evident in 6 out of 14 cases (42.9%). From urinary excretions following the administration of Saiboku-to, we detected the magnolol component of magnoliae cortex. Effective cases showed increased free magnolol in urine, suggesting the value of combined magnolol as a clinical parameter. We also investigated the function of 11β-hydroxysteroid dehydrogenase (11-HSD) inhibition, one of the mechanisms of the steroid-sparing effect, in healthy subjects using three Saiko-zai. Saiboku-to lowered the activity of 11-HSD and increased the concentration of prednisolone (PSL), while Sairei-to had no influence on the metabolism of PSL. Shosaiko-to, on the other hand, increased the activity of 11-HSD and lowered the concentration of PSL. Thus the three Saiko-zai showed different results.