Consecutive prospective coronary angiographies following 24 hours were studied to find early angiographic predictors of post-PTCA restenosis in the follow-up of 71 patients who had been dilated successfully. Conventional cine coronary and quantitative digital angiography was used to analyse the degree of obstruction previous to dilatation following 24 hours and 30 minutes after the procedure. Following 24 hours, angiographic findings showed: Group A: patients having the same lumen as at immediate post-PTCA time (65.9%); Group B: patients with 20% or more immediate post-PTCA time (21.5%). Group C: patients with total obstruction of vessel (12.6%). The basal clinical conditions were similar in the three groups. The degree of basal obstruction and the clinical findings were similar in the three groups; the dilated arteries in Groups A and B were similar and total occlusion before PTCA was more frequent in Group C than in B and A; 30 minutes post PTCA lesions in group A had less residual stenosis than group B (p less than .01) and C (p = NS), this difference increased significantly (p less than .0001) at 24 hours and in the late follow-up. In the follow-up (means 6.4 months) there was total restenosis per lesion in 32.9%. In Group A, there was 8.6%; in Group B, 68.4% (p less than .0001) and in Group B plus C, 80%. Patients with more than 10% obstruction had a greater degree of restenosis (43.9%) than when the initial lesion was less than 10% (23.4%).(ABSTRACT TRUNCATED AT 250 WORDS)