The aim of the present study was to assess the long-term clinical course of patients with syndrome X, focusing on different courses between exercise-induced ST depression and chest pain. Forty-three patitheents with syndrome X were followed up for 6.4 ± 3.8 years. They were divided into the 3 groups according to chest pain: disappeared (n = 24), improved (n = 14), or unchanged (n = 5). No patients had cardiac events and all had a favorable long-term prognosis. In patients showing disappearance of chest pain, exercise-induced ST depression and rate-pressure product (RPP) at peak exercise did not change during follow-up. However, ST depression and RPP decreased significantly in those with improved chest pain. These observations suggest that abnormal pain perception plays an important role in the development of chest pain.