Introduction: We present the results of a pilot study performed in 5 female patients with overactive bladder symptoms (OAB), combined with urethral instability, treated with subtrigonal Botulinum toxin-A (BoNT-A) injections. Treatment modalities for OAB have in common that they interfere in any part of efferent and afferent signaling from the bladder to the brain, the difference is in the localization and extent of interference. We hypothesized that patients with OAB symptoms and UI could benefit more from a treatment with the mode of action at the urodynamically identified problem. Methods: This is a retrospective description of the pilot study we performed. Four patients had a long history of refractory idiopathic OAB symptoms, in one patient the main complaint was painfull bladder syndrome. In all patients UI was demonstrated during filling cystometry. Treatment was started with subtrigonal injections of 10cc lidocaine 1%. If OAB symtoms improved with more than 50%, treatment continued with subtrigonal injections with BoNT-A. Results: Four out of 5 patients OAB symptoms improved more than 50% after subtrigonal BoNT-A injections. UI disappeared in one patient after treatment. In three other patients, the maximum amplitude of the urethral pressure variations decreased from more than 40cm H2O up to a maximum of 20 cm H2O. The most remarkable change was the improvement in first sensation of filling. Conclusion: Chemical denervation by subtrigonal BoNT-A injections in patients with OAB combined with UI, resulted in improvement of refractory OAB symptoms in all patients with refractory OAB as main complaint in this study.