The urodynamic study of 31 patients suffering from urinary incontinence after prostatic adenomectomy showed us that there were 3 groups of patients very different in terms of symptoms and treatment: some had a low flow rate with an obstructive syndrome necessitating the treatment of the "obstacle"; others had a low flow rate and poor detrusor contraction and the last group had a high flow rate. Those two groups often need an artificial sphincter. The study is being continued in order to define a preoperative criterion of the risk of incontinence.