Silent ischaemia has been widely investigated limiting the diagnostic approach to the left ventricle. To date, no systematic study on silent ischaemia in patients with demand-induced right ventricular dysfunction has been reported. The occurrence of painless ischaemic episodes was evaluated by atrial pacing and radionuclide angiography in 20 consecutive patients with single right coronary artery stenosis and without previous myocardial infarction. At the peak pacing rate all patients showed transient myocardial dysfunction (reduction of ejection fraction and/or development of wall-motion abnormalities) localized to the right, the left, or to both ventricles in 9, 1 and 10 patients, respectively. Eight patients experienced chest pain (group 1) and 12 were asymptomatic (group 2) at the maximal pacing rate. Basal left ventricular ejection fraction (55 +/- 4% vs. 55 +/- 5%), basal right ventricular ejection fraction (48 +/- 4% vs. 46 + 8%), peak pacing left (52 +/- 9% vs. 50 +/- 11%) and right (38 +/- 7% vs. 37 +/- 9%) ventricular ejection fractions, and maximal pacing pressure rate product (17,289 +/- 2880 vs. 19,244 +/- 3806) were not significantly different in the two groups. This study demonstrates a high prevalence of silent ischaemia in patients with single right coronary artery stenosis and pacing-induced dominant right ventricular dysfunction. Painful episodes do not appear to be related to the magnitude of changes in ejection fraction.