AIMS: Pulmonary vein isolation (PVI) is the cornerstone of catheter ablation of atrial fibrillation (AF). The intervenous ridge (IVR) may be incorporated into ablation strategies to achieve PVI; however, randomized trials are lacking. We performed a randomized multi-centre international study to compare the outcomes of (i) circumferential antral PVI (CPVI) alone (minimal) vs. (ii) CPVI with IVR ablation to achieve individual PVI (maximal). METHODS AND RESULTS: Two hundred and thirty-four patients with paroxysmal AF underwent CPVI and were randomized to a minimal or maximal ablation strategy. The primary outcome of recurrent atrial arrhythmia was assessed with 7-day Holter monitoring at 6 and 12 months. PVI was achieved in all patients. Radiofrequency ablation time was longer in the maximal group (46.6 ± 14.6 vs. 41.5 ± 13.1 min; P < 0.01), with no significant differences in procedural or fluoroscopy times. At mean follow-up of 17 ± 8 months, there was no difference in freedom from AF after a single procedure between a minimal (70%) and maximal ablation strategy (62%; P = 0.25). In the minimal group, ablation was required on the IVR to achieve electrical isolation in 44%, and was associated with a significant reduction in freedom from AF (57%) compared with the minimal group without IVR ablation (80%; P < 0.01). CONCLUSION: There was no statistically significant difference in freedom from AF between a minimal and maximal ablation strategy. Despite attempts to achieve PVI with antral ablation, IVR ablation is commonly required. Patients in whom antral isolation can be achieved without IVR ablation have higher long-term freedom from AF (the Minimax study; ACTRN12610000863033).