Hot (44) and cold (30) caloric test are the most common tool to investigate canal activity. Many authors, otherwise, have pointed out that this method is very long needing about five minutes of interval among the irrigations and that it is often troublesome for the patient that is exposed four times to a vertigo. To investigate vestibular function some of these authors tried to use the hot monothermal test alone but results were poor. The aim of this study was to propose a shorter and a less troublesome method of investigation and to introduce a new diagnostic possibility not pointed out with traditional caloric test. We have tried to determine some new reliable diagnostic criteria modifying confidential value of the hot monothermal test and considering the eventual presence of the nystagmus and its direction during the cold simultaneous test; on the basis of this results we are able to distinguish a normal vestibular function from a labyrinthine preponderance or a directional preponderance or an aspecific disfunction. When the vestibular function is normal or when there is a labyrinthine preponderance our results are in total accord with those achieved with the traditional bithermal test. Therefore we suggest to use always the hot monothermal test associated with the cold simultaneous test, performing the two cold irrigations in additions, only in the case of a directional preponderance or an aspecific disfunction.