Thirteen of 41 patients (32%) with Williams syndrome in a multidisciplinary clinic were noted to have genitourinary symptoms. The predominant features were increased urinary frequency and daytime wetting. Four patients had bladder diverticula and uninhibited detrusor contractions as demonstrated on urodynamic studies. We speculate that there may be an association between increased detrusor pressure, an abnormal bladder matrix, and the presence of diverticula. Early detection of urinary dysfunction through clinical symptoms and appropriate urodynamic studies, with institution of bladder training and anticholinergic medication can improve the patients' voiding patterns, both medically and socially.