Objectives The arterial pressure-volume index (API) is a non-invasive assessment of arterial stiffness, and is suggested as a useful predictor of future cardiovascular events. The aim of the present study was to determine the effects of low-frequency and low-intensity ultrasound applied to the forearm for 10 min on the API in Japanese subjects with type 2 diabetes and hypertension. Methods We examined the effects of low-frequency and low-intensity ultrasound (800 kHz, 25 mW/cm2) applied to the forearm for 10 min on the API, blood pressure (BP) and pulse rate in 40 Japanese subjects (13 men and 27 women
mean age ± SE, 70 ± 2 years) with type 2 diabetes and hypertension, who had the API &gt
 30 and systolic BP &gt
 140 mmHg at a clinic visit. We also examined the effects of the ultrasound irradiation for 10 min on the API, BP and pulse rate in 33 Japanese subjects (11 men and 22 women
mean age ± SE, 65 ± 2 years) with type 2 diabetes and hypertension, who had the API &gt
 30 and systolic BP (SBP) &lt
 140 mmHg. Results The API, systolic BP and pulse rate in the ultrasound treatment group was significantly lower than the baseline values in the subjects who had the API &gt
 30 and either the baseline of systolic BP &gt
 140 mmHg or systolic BP &lt
 140 mmHg. Conclusions The low-frequency and low-intensity ultrasound irradiation to the forearm for 10 min might be useful as a preventive application for arterial stiffness in subjects with type 2 diabetes and hypertension.