Introduction and Objectives: There is a paucity of data comparing the left radial approach (LRA) and right radial approach (RRA) for percutaneous coronary intervention (PCI) in all-comers populations and performed by operators with different experience levels. Thus, we sought to compare the safety and clinical outcomes of the RRA and LRA during PCI in "real-world" patients with either stable angina or acute coronary syndrome (ACS)., Methods: To overcome the possible impact of the nonrandomized design, a propensity score was calculated to compare the 2 radial approaches. The study group comprised 18 716 matched pairs with stable angina and 46 241 with ACS treated with PCI and stent implantation between 2014 and 2017 in 151 tertiary invasive cardiology centers in Poland (the ORPKI Polish National Registry)., Results: The rates of death and periprocedural complications were similar for the RRA and LRA in stable angina patients. A higher radiation dose was observed with PCI via the LRA in both clinical presentations (stable angina: 1067.0±947.1 mGy vs 1007.4±983.5 mGy, P=.001; ACS: 1212.7±1005.5 mGy vs 1053.5±1029.7 mGy, P=.001). More contrast was used in LRA procedures but only in ACS patients (174.2±75.4mL vs 167.2±72.1mL, P=.001). Furthermore, periprocedural complications such as coronary artery dissection (0.16% vs 0.09%, P=.008), no-reflow phenomenon (0.65% vs 0.49%, P=.005), and puncture site bleeding (0.09% vs 0.05%, P=.04) were more frequently observed with the LRA in ACS patients. There was no difference in mortality between the 2 groups (P=.90)., Conclusions: Our finding of poorer outcomes with the LRA may be related to lower operator experience with this approach. While both the LRA and RRA are safe in the setting of stable angina, the LRA was associated with a higher rate of periprocedural complications during PCI in ACS patients., (Copyright © 2020 Sociedad Española de Cardiología. Published by Elsevier España, S.L.U. All rights reserved.)