Objective: The effect of the KCNQ modulator retigabine on rat detrusor function was investigated in vitro and in vivo to assess the potential of KCNQ openers for treatment of over-active bladder. Methods: The effect of retigabine (10 mg·kg^-1, p.o.) on cystometric parameters was measured in conscious rats with capsaicin irritated bladders. In organ bath studies, urinary bladder rings were exposed to retigabine and the effect on parameters from myography experiments was evaluated. The bladder rings were stimulated with electric field, capsaicin and carbachol in order to affect the parasympathetic nerve endings, the efferent nerves and muscarinic receptors on the smooth muscle tissue, respectively. Results: Retigabine (p.o.) relaxed rat urinary bladders in vivo and decreased micturition pressure by 63% and 54% during saline (p=0.016) and capsaicin (p=0.035) infusion, respectively, compared to vehicle. In bladder organ bath, retigabine potently relaxed the bladder rings with an EC50 ranging from 5.0 to 9.7 mM in the capsaicin, carbachol and EFS protocol. Conclusion: These results suggest that retigabine and other KCNQ openers may have beneficial effect on bladder over-activity.