Intracoronary injection of a vasodilator agent in an almost systematic practice during coronary angiography or angioplasty because of the dynamic information that it provides concerning the stenosis, the artery in the unstenosed segment and spastic phenomena. Nitroglycerin is the reference drug with, however, a significant dose-dependent hypotensive effect. The aim of this randomised open trial was to compare the effects of Linsidomine, the active metabolite of molsidomide with the reference product. Eighty patients aged 59.2 +/- 10.4 years received either 0.15 mg of nitroglycerin or 0.8 mg of linsidomine during coronary angiography. Aortic pressure and heart rate were monitored continuously over 3 minutes; at the 3rd minute and injection of contrast was performed under fluoroscopic control under the same conditions as the basal injection for an experienced coronary angiographist to judge semi-quantitatively the quality of vasodilation at the site of stenosis and in the whole artery. In the linsidomine group, the only significant change was a moderate fall in systolic pressure from the 1st to the 3rd minute. In the nitroglycerin group, all pressure parameters fell from the 30th second. The heart rate remained stable in both groups. The maximal pressure differences were significantly different in the two groups: -4 +/- 7.3 mmHg versus -11.3 +/- 9.2 mmHg (linsidomine versus nitroglycerin), p less than 0.001 for systolic pressure; -0.1 +/- 5 mmHg versus -3 +/- 5.4 mmHg respectively for diastolic pressure (p less than 0.05); and -1 +/- 6 mmHg versus -5.3 +/- 6.4 mmHg (p less than 0.01) for mean pressure. These pressure changes were not associated with any detectable untoward clinical effect in either group of patients.(ABSTRACT TRUNCATED AT 250 WORDS)