In humans, urethral fibrosis and sphincter incompetence commonly are associated in the genesis of stress incontinence. Other factors are often associated, such as bladder hyperactivity and increased demand on the sphincter mechanism created by contracted or large atonic bladder or polyuria. The frequent association of several factors and the limited information given by the classical methods suggest a need for the routine use of objective urodynamic studies in the assessment of stress incontinence in patients. A more conservative, better oriented, therapeutic approach may result from this concept.