Electromyographical activity of various perineal striated muscles during bladder filling and voiding has been studied. These muscles provoke a urethral pressure of 10 to 20 mm. Hg. Initiation of micturition can be characterised either by a progressive or an abrupt inhibition of perineal muscle activity or by a transient promotion of activity. The former features are more frequently observed in spontaneous voiding, the latter in voluntary voiding efforts with low vesical volumes. Voiding is possible without complete inhibition of myographical activity. In pathological cases (obstruction and neurogenic bladders) dyssynergy between the detrusor and the external striated sphincter may occur. Moreover, we found that a inco-ordination of various striated pelvic floor muscles may also be present. Such dyssynergism may cause functional obstructions with residual urine, spurting, dysuria and pseudo-incontinence.