Introduction and hypothesis The purpose of the study was to investigate the relationship of diabetes mellitus and urinary incontinence in adult women. Methods We conducted a cross-sectional, comparative study with a case-control design. One thousand three hundred eighty-one women (aged 20-87 years) attending six Primary Healthcare Centers in Turkey were enrolled in this study, after giving their informed consent. Subjects were dichotomized into cases and controls according to presence of diabetes mellitus (DM) and were matched for the confounding factors age, body mass index (BMI), and reproductive history. Results Nine hundred ten women were included: 273 diabetics and 637 non-diabetics. Diabetes was shown to be associated with a 2.5-fold risk increase for urinary incontinence (UI), and age and BMI were weakly associated with UI. UI was significantly more prevalent in diabetic women: 41% diabetic and 22.1% non-diabetic women reported UI (p<0.001). Age, BMI, and DM were revealed as independent determinants of UI in adult women. Urge incontinence was more prevalent in nondiabetic women, whereas stress and mixed incontinence were more prevalent among diabetic women. Conclusions DM is the most important independent determinant of UI.