INTRODUCTION The prevalence of obesity has been rising sharply in industrialised countries over the past decade. As the Body Mass Index (BMI) is recognized as an accurate and objective measurement of individual body mass, this study investigated whether BMI is associated with lower urinary tract symptoms in women. MATERIALS AND METHODS This retrospective study analysed a database of 750 female patients who were referred to the Uro-Gynaecology Unit from 2002 to 2004 because of urinary and sexual disturbances. Patients were divided into four classes (I, II, III, IV). Each class was analysed as a function of the following variables: type and grade of urinary incontinence, number of daily pads, irritative symptoms, sexual activity, micturitional urgency or detrusor hyperactivity, urine leakage during urodynamics testing while coughing or performing Valsava's manoeuvre, dysuria, abdominal straining, stop-go micturition, feeling of incomplete bladder emptying, feeling of perineal heaviness, hypovalid stream, constipation, grade and type of urogenital prolapse. RESULTS In BMI class I did not complain of urinary incontinence. 155 70.8% referred urinary leakage while coughing or under physical effort. In Class II BMI 78.9% referred urinary incontinence. The incidence rose as the BMI increased. In BMI class III, 95.1% referred urinary incontinence and all 16 patients in BMI class IV were incontinent. CONCLUSIONS Obese women are more prone to urinary incontinence which has a negative impact on the patient's quality of life and depression status. Mental status as well as anatomic deficits may explain the relationship between obesity and incontinence.