The propensity of Māori towards violence and aggression has been assigned to the expression of a unique monoamine oxidase gene (MAO) popularly known as the ‘Warrior Gene’. This assignment suggests that the violence supposedly exhibited by Māori is due to the very nature of Māori himself. Although this assignment and assessment by Pākehā falls into the usual pattern of stereotypes offered about Māori over the last 200 years, it is instructive to examine the truth of the matter, since it was based on the results of a scientific investigation. Behavioural problems have been reported in people who have exhibited abnormalities in the expression of unusual forms of MAO genes and their conditions have been variously described as diseases. Could those Māori who express the ‘warrior’ gene be diagnosed as having a medical condition similar to those with diseases such as Brunner syndrome or Norrie disease, two diseases involved in the expression of abnormal MAO genes? As a consequence is being Māori just another disease?