The aim of this study was to assess the effects of coronary angioplasty on the intima with respect to the duration of balloon inflation by percutaneous angioplasty. Twenty-seven patients were randomized according to the total duration of balloon inflation: Group I "standard" duration (total duration < or = 3 min, N = 13) and Group II: prolonged duration (total duration > or = 12 min, N = 14); the type and distribution of the lesions were comparable in the two groups. The results of angioplasty were evaluated immediately after dilatation by angiography and angioscopy. Angioscopy was performed without failure or complications with perfect definition of the images in all cases. Angioscopy showed 1) intimal tears, 2) thrombi, 3) longitudinal dissections. A classification in three grades was used taking the apparent gravity of the lesions into consideration. The mean duration of balloon inflation in Group I was 205 +/- 45 s and 958 +/- 129 s in Group II. The residual stenosis was 36 +/- 8% in Group I and 26 +/- 10% in Group II (p < 0.05). Angioscopy showed the frequency of intimal tears to be twice greater in Group I (9 cases) than in Group II (4 cases) (p = 0.05). Intravascular thrombi were observed in 13 cases, 6 in Group I and 7 in Group II. One case of longitudinal dissection was observed in each group: only one of these two cases was detected at angiography. The authors conclude that repeated and prolonged balloon inflations improve the immediate results of angioplasty with less residual stenosis at angiography and a lower incidence of intimal tears at angioscopy.