Adenosine is formed from adenosine triphosphate within the ischaemic cells from where it is released into the coronary circulation. Adenosine exhibits several cardiovascular effects which tend to protect the ischaemic myocardium. Based on the observation that in healthy volunteers the intravenous infusion of adenosine produces angina-like chest pain, it has been recently proposed that another cardioprotective action of this substance could be provocation of angina. If this is the case adenosine should not produce chest pain in patients with silent ischaemia. To test this hypothesis we infused this substance intravenously at increasing doses of 50, 100, 150, 200, 250 and 300 micrograms kg-1 min-1 in eight patients with silent ischaemia (group A). All of them developed ST depression (1.8 +/- 0.2 mm) during exercise testing and seven also during adenosine infusion (1.1 +/- 0.8 mm). However, none of the patients had chest pain during exercise while seven had chest pain during adenosine. We then infused adenosine in eight other patients (Group B) who had painful ischaemia and an exercise tolerance similar to that of Group A patients (time to 1 mm ST depression 8.6 +/- 2.7 min and 8.4 +/- 3 min, respectively, P = NS). Adenosine induced chest pain in all Group B patients. The time to pain onset during adenosine was similar in the two groups (9.3 +/- 2.3 min in Group B and 12.4 +/- 4.9 min in Group A).(ABSTRACT TRUNCATED AT 250 WORDS)