An association between ergot-derived dopamine agonists and asymptomatic valvular heart disease in Parkinson's disease has been established. For safe use of these agonists, it is important to specify those at high risk for valvular heart disease among patients with Parkinson's disease. We performed a nested case-control study of 223 patients with Parkinson's disease. In results of multivariable logistic analyses, use of pergolide, use of cabergoline, age, male sex, and hypertension were independent significant risk factors for left-sided valvular regurgitation. In patients receiving cabergoline or pergolide, elderly (>or=70 years) hypertensive patients had a markedly high risk for valvular regurgitation (odds ratio 94.5) as compared to non-elderly (<70 years) patients without hypertension. The risk of valvular regurgitation caused by pergolide or cabergoline was found to be highly enhanced by comorbid hypertension or aging, suggesting that special attention should be paid when prescribing cabergoline or pergolide for those patients.