A 65-year-old woman was referred to our hospital for an intensive medical check-up due to chest tightness, which was aggravated by effort particularly while carrying heavy baggage or using her upper extremity. She had a history of coronary artery bypass grafting 8 years previously with left internal thoracic artery (LITA) to the left anterior descending artery (LAD). The resting electrocardiogram showed widespread ST depression. Coronary angiography showed that the bypass graft was patent (Panel A, LITA-LAD: left internal thoracic artery to left anterior descending artery). However, the proximal portion of the left subclavian artery showed severe arteriosclerotic stenosis (Panel A, arrow), which appeared to be the cause of angina pectoris. In order to evaluate the myocardial ischaemia induced by left upper extremity exercise, we performed an electrocardiogram during the hand grip-exercise test (Panel B). While there was no significant ST-T change on the electrocardiogram during the right hand grip-exercise test (Panel C, Hand grip-exercise test, Before treatment, Rt), the left hand grip-exercise test induced further marked ST depression (Panel C, Hand grip-exercise test, Before treatment, Lt), indicating that coronary-subclavian artery steal phenomenon during left upper extremity loading induced myocardial ischaemia due to decreased blood flow to the LITA, which was also confirmed by stress myocardial scintigraphy. Angioplasty to treat the stenosis located in the left subclavian artery was performed. After the catheter treatment, ischaemia could no longer be induced during the left hand grip-exercise test (Panel C, Hand grip-exercise test, After treatment, Lt). Moreover, her symptoms disappeared and ST depression observed on the resting electrocardiogram markedly improved (Panel C, 5 days after treatment, rest). This case suggests that the hand grip-exercise test is a very simple and useful method to evaluate myocardial ischaemia in patients who underwent coronary bypass surgery with the internal thoracic artery and are suspected of suffering from coronary-subclavian artery steal syndrome.