Abstract Introduction Ranolazine is a late sodium current blocking drug developed as an antianginal agent, with good preliminary efficacy data even for antiarrhythmic purposes (both at atrial and at ventricular level). Objectives To evaluate patients’ clinical characteristics and antiarrhythmic efficacy of ranolazine in subjects with a history of atrial and/or ventricular arrhythmias, isolated or repetitive. Patients and methods we included patients who received a first prescription of ranolazine for antiarrhythmic purposes in our center from 1/2022 to 11/2023 and evaluated the survival free from major arrhythmic relapses/ablation. Results 93 patients were enrolled (66±13 years, 15% women): 59% with arterial hypertension, 26% diabetics, 46% with post–ischemic dilated heart disease, 32% with primary cardiomyopathy (including 11% with hypertrophic cardiomyopathy, 10% with LMNA, 14% with TTN), 46% with implantable cardioverter defibrillator, 9% with pacemaker. The mean LV ejection fraction was 42 ± 15%, the mean serum creatinine 1 ± 0.3 mg/dL. Half (50%) had a history of atrial arrhythmias in the 6 months before starting the drug, mainly paroxysmal atrial fibrillation (AF), 67% of ventricular arrhythmias (VAs), mainly isolated and repetitive premature ventricular beats (PVB, 47% of the total), but also sustained or treated VAs (n=18, 19%). Overall, 18% of patients had already undergone AF ablation, 13% ventricular tachycardia ablation, 3% cardiac sympathetic denervation. Finally, 95% of patients were on beta–blocker therapy and 28% were on amiodarone. Ranolazine was prescribed at an average initial dose of 535± 150 mg. The majority (54%) of patients (n=50) had a follow–up longer than 3 months (median 9 months, IQR 6–14); in 6% the drug was stopped due to intolerance and the average dose at the last FU was 641 ± 150 mg. Twenty–eight percent of patients with paroxysmal/persistent atrial arrhythmias had relapses, requiring ablation in 6%. Among patients with major VAs, 57% suffered recurrences, but only 19% required ablation (invasive in 2 cases, non–invasive in 1 case). Finally, among the patients with PVBs, none suffered major VAs or required PVB/VA ablation. Conclusions This is the largest available case–series reporting about the real–world usage of ranolazine for antiarrhythmic purposes. Our single center experience supports ranolazine’s good safety and tolerability and shows encouraging efficacy results in terms of clinical stabilization of complex patients.