This study summarises the authors' experience of the prediction of primary success of coronary balloon angioplasty. A qualitative and quantitative angiographic study of 3679 coronary stenoses was undertaken before and after dilatation. Total occlusions before angioplasty and dilatations of saphenous vein bypass grafts were excluded. Two parameters were noteworthy: the occurrence of acute occlusion of the lesion during or immediately after angioplasty and the degree of residual stenosis as assessed by quantitative angiography. After multivariate analysis, 3 factors seemed strongly predictive of the risk of acute occlusion: the percentage stenosis before angioplasty, a left coronary artery stenosis and stenosis situated at the point of angulation of an artery. Quantitative angiographic studies identified 4 factors predictive of significant residual stenosis: the percentage stenosis before angioplasty, the irregularity of the contours of the lesion stenosis situated at the point of angulation of an artery and the presence of calcification. This study therefore shows at least two important discordances with the ACC/AHA morphological classification of coronary stenosis: firstly, excentricity would not seem to be a risk factor for primary failure of angioplasty and, secondly, excluding total occlusions, the percentage coronary stenosis before angioplasty as assessed by quantitative coronary angiography would seem to be the main predictive factor of both the risk of occlusion and the degree of residual stenosis.