Unstable bladder symptomatology often includes different types of urinary incontinence. We assessed the possible correlation between urinary incontinence associated with an unstable bladder and pelvic floor activity. In addition, we assessed when oxybutynin administration has favourable effects on urinary incontinence associated with an unstable bladder. Sixty female patients affected by an unstable bladder, consecutively enrolled in the study, were evaluated by means of urodynamics and diagnostic electromyography. Urinary incontinence, when present, was characterized. Possible correlation between types of urinary incontinence and types of pelvic floor dysfunction was investigated. Oxybutynin 5 mg.x3/day was administered per os. Drug activity was evaluated in terms of outcome for the different types of urinary incontinence. A prevailing reduction in maximal muscle contraction and endurance in the patients affected by stress and mixed urinary incontinence was found. 42% of the patients affected by urge incontinence showed a decrease in endurance, and 52% showed overall good functioning of their pelvic floor. Administration of oxybutynin only improved urinary incontinence in those patients affected by urge incontinence who did not have pelvic floor dysfunction (exact Fisher’s test, p<0.001).