The improvement of ventilatory function by spa therapy was examined in 37 patients with steroid-dependent intractable asthma (SDIA) in relation to clinical asthma types. All subjects had been on long-term corticosteroid therapy before spa therapy. Spa therapy was found to improve the values of ventilatory parameters. The percent improvement in all subjects was +4.1% in %FVC, +8.9% in FEV1.0%, +9.8% in %PEFR, +22.0% in %MMF, +19.7% in %V50 and +28.2% in %V25, respectively. Relating to clinical asthma types, moderate improvement in %MMF and %V25 from 16.7% to 16.9% was observed in type Ia cases, and marked increase in %MMF, %V50 and %V25 was observed from 42.2% to 43.2% in type Ib cases. However, no significant increase was found in these parameters of types Ia or Ib after spa therapy. In patients with type II, a significant increase was shown in %V50 (p less than 0.05) and %V25 (p less than 0.01) after spa therapy. The results show that spa therapy improves the condition of small airways disorder in patients with SDIA.