Waon therapy is a form of thermal treatment in a dry sauna maintained at a temperature of 60°C, which differs from the traditional sauna. Waon therapy reportedly improves the hemodynamics, cardiac function, ventricular arrhythmias, vascular endothelial function, neurohormonal factors, sympathetic nervous system function, and symptoms in patients with chronic heart failure (CHF). It has also been demonstrated that the molecular mechanism by which Waon therapy improves vascular flow and endothelial function involves increased expression of endothelial nitric oxide synthase (eNOS). Furthermore, in a mouse model of hindlimb ischemia, repeated Waon therapy increased eNOS protein expression, blood flow, and capillary density. Moreover, Waon therapy did not increase blood flow and capillary density in eNOS-deficient mice, indicating that eNOS is a critical regulator of the angiogenesis induced by this therapy. Moreover, repeated Waon therapy is effective for patients with severe peripheral arterial disease (PAD), as evidenced by substantial decrease in pain scores, increases in both ankle-brachial pressure index and blood flow assessed by laser Doppler perfusion imaging, and by formation of new collateral vessels on angiography. In addition, ischemic ulcers heal or improve markedly. In conclusion, Waon therapy is an innovative and highly promising strategy for treating CHF and PAD. (Circ J 2010; 74: 617-621)