The striated musculature of the pelvic floor is a structure of great importance in the mechanism of urinary incontinence in women. The anus' elevator muscle is one of the main parts of the pelvic floor, having a preponderant part in the anatomical support of the bladder neck and proximal urethra. The peri-urethral striated muscle is also important in the maintenance of the intra-urethral pressure. We know that obstetric trauma, the low level of estrogen in consequence of menopause and vaginal surgeries may cause stress urinary incontinence (SUI) and genital prolapse, due to neuro-muscular compromising of the pelvic floor. The pelvic floor function is fundamental in the maintenance of urinary incontinence, and compromising this, it may be responsible for an index of 25 to 30% of non-success in surgical treatment of SUI, independent of the surgical technique used or the ability of the surgeon. So, the functional evaluation of the pelvic floor is a prognostic factor in the treatment of SUI. In the cases of important muscular compromise, the treatments with physiotherapeutic techniques do not present favorable results. Besides that, the patients with an important dysfunction of the pelvic floor musculature, even in the absence of SUI type III, may benefit more with a surgical therapeutic (facial sling or TVT), once they are independent of the pelvic floor musculature for anatomic support of the bladder neck. So, pelvic floor functional evaluation must be done before instituting treatment in women with SUI. It may be done through an electromyography (golden stand), a histomorphology study through a muscular biopsy or a clinical evaluation through a digital vaginal palpation, perineometer and vaginal cones. Among them, vaginal exploration is a simple method that does not need any instruments; it may be done using a functional evaluation of the musculature of the pelvic floor (AFA) graduating it from 0 to 4, in accordance to the contractile activity of this musculature evaluated by digital palpation. In our experience, we showed, studying 25 patients with SUI submitted to the treatment with vaginal cones, that, the only patient that did not improve showed a deficient functional evaluation of the pelvic floor (AFA=0). This muscular dysfunction was verified with a biopsy of the pubococcigeo muscle that showed an important degeneration of the musculature and a fat and collagen deposit.