Ambulatory monitoring has been hailed as the 'way forward' in urodynamic investigation. Its introduction has caused much excitement and there is no doubt that it detects more abnormalities than does conventional cystometry. It is, however, labour intensive and time consuming for both operator and patient, and requires commitment from both to be successful. No standards have been set as to how long a test ought to last, how many voids are required and how to interpret traces. To date the standard cystometric criteria of normality have been applied, but this would appear to be inappropriate. Several commercial companies have developed systems and are marketing them widely as an adjunct, or alternative, to conventional cystometry. It is recommended that before this technique is introduced into routine clinical practice it is fully evaluated, with standardization of terminology relating to its use.