Simplicity is the Ultimate Sophistication. Leonardo de Vinci Three decades ago, the Institute of Medicine promoted guideline development to improve the quality of clinical care and patient outcomes. 1 Clinical guidelines for atrial fibrillation ablation, like all guidelines in cardiovascular medicine, are developed by professional societies primarily to guide decision-making. They provide approaches for the diagnosis, management, and prevention of specific diseases or conditions after a thorough and systematic review of the best available scientific evidence. Robust methodologies for guideline development have evolved with common elements including the familiar class I, IIa, IIb, and III recommendations. Evidence-based medicine is the basis for classification of level of evidence (LOE). LOE A is defined by data from multiple randomized controlled trials (RCTs), meta-analyses of RCTs, or one or more RCT corroborated by high-quality registry studies. Level B refers to moderate-quality evidence from one or more RCT or meta-analyses of moderate-quality RCTs. Evidence classified as B further is categorized as randomized (R) or nonrandomized (NR).