ntroduction: To compare the safety and efficacy of posterior tibial nerve stimulation (PTNS) versus an intradetrusor injection of botulinum toxin type-A (BTX-A) 100 U in the management of refractory idiopathic overactive bladder (OAB). MATERIALS AND METHODS: We randomized 60 patients with refractory idiopathic OAB to receive an intradetrusor injection of BTX-A 100 U or PTNS. We assessed the patients at baseline, 6 weeks, 3 months, 6 months, and 9 months, and determined their clinical symptoms, overall OAB symptom score, urgency score, quality-of-life score, and urodynamic study parameters. RESULTS: The two patient groups had similar baseline characteristics. After treatment, the patients in the BTX-A group had significant improvements in all parameters compared to their baseline values. Patients in the PTNS group initially had significant improvements in all parameters, but by 9 months, this was no longer true for most parameters. In general, the improvements were more significant in the BTX group, especially at 9 months. In the BTX-A group, two patients (6.6%) needed clean intermittent catheterization; 3 patients (2 women and 1 man; 10% of patients) had mild hematuria, and 2 patients (6.6%) had urinary tract infections (UTIs). In the PTNS group, local adverse effects included minor bleeding spots and temporary pain. CONCLUSIONS: Intradetrusor injection of BTX-A and PTNS are both effective to manage refractory idiopathic OAB. BTX-A is more effective than PTNS and is also durable, minimally invasive, reversible, and safe, but it also has more side effects.