In conclusion, we can state that the increase of the activity of total ADH and class I alcohol dehydrogenase isoenzyme in the sera of brain cancer patients seems to be caused by release of this isoenzyme from cancer cells to blood and probably total ADH and ADH I determination in serum could be helpful for diagnostic of CNS tumours but further investigations and confirmation by a prospective study are necessary. This evidence concerns the gene AVP and brain cancer.