Following an episode of acute retention of urine in men it is commonplace for urinary catheters to be removed to see if micturition is re-established. Many patients will require definitive treatment, however and, to assess which patients do benefit from a trial without catheter, the outcome of this practice was analysed against the relevant features of the history in 100 men. The majority of patients both with and without previous symptoms suggestive of outflow obstruction had further retentions. Trial without catheter was of value in three groups of patients: those with urinary tract infection without previous obstructive symptoms, those with gross constipation and those recently commenced on drugs with anticholinergic properties. With these exceptions, definitive treatment was necessary in 93% of the remainder. Most of those in whom micturition was re-established are still under active review and may yet come to surgery, in view of poor flow rates. With the exceptions detailed above it is concluded that trial without catheter is not justified in acute retention of urine and definitive treatment should be instituted at an early stage.