Eight cases of vesico-sphincteric disorders (dysuria and chronic retention of urine) observed after spinal anaesthesia are reported. These symptomatic disorders were caused by a peridural haematoma in 3 cases and by lack of bladder contraction due to an "exhausted detrusor muscle" in 5 cases. The mechanism of the disorders (predominant vesical hypoactivity with sensory disorders) is discussed. The usefulness of urodynamic investigation in determining the physiopathological mechanism(s) and that of electrophysiological exploration in the search for a neurogenic disease is emphasized, as is the need for a preventing treatment (intermittent catheterization) in case of forced bladder detected by systematic recording of postoperative micturitions.