AbstractTo examine the balloon inflation pressures required for successful percutaneous transluminal coronary angioplasty (PTCA), the maximal inflation pressure required for 477 coronary lesions in 200 consecutive patients was determined retrospectively. When graded balloon infaltions just sufficient to achieve full expansion were used, the maximal inflation pressure used was ≤8 atm in 412 stenoses (86%) and was ≤10 atm in 463 stenoses (97%). Successful PTCA was achieved in 98% of lesions with a 3.5% major procedural complication rate. In a second group of 100 patients studied prospectively, the inflation pressure required to achieve full balloon expansion was ≤8 atm in 214 of 232 stenoses (92%) and ≤10 atm in 228 stenoses (98%). Thus, PTCA of coronary stenoses can be achieved with high success rates and low complication rates when graded inflations to pressures just sufficient to achieve full balloon expansion are performed. Most coronary stenoses will respond to pressures ≤8–10 atm.