The purpose of this thesis was to investigate prediction of senior leader transformational leadership behaviour. Transformational leadership was identified as a major theory with substantial practical implications for economic prosperity. It was argued that a better understanding of what predicts transformational behaviour would assist in creating a lift in the effective application of the theory with attendant benefits for all organisational stakeholders. It was proposed that personality components would predict transformational behaviour. Personality was conceptualised in two ways: as components of the Five Factor Model of personality and as personality disorder components. Specifically, eight personality constructs were hypothesised as predictors. They were three Hogan Personality Inventory based Five Factor Model components and the five Hogan Development Survey personality disorder components. It was further proposed that self-subordinate rating agreement would moderate the prediction of transformational behaviour by the selected personality components. A survey research methodology was used to gather data from senior Australian organisational executive leaders. Two samples were accessed while subjects were attending training or strategy seminars. The samples incorporated a total of 462 individual senior leader subjects and 1,881 of their subordinates drawn from the top four levels of a range of large multi-level public and private Australian organisations. It was argued that the sample validly represent a senior executive cohort of organisational leaders. Subject leaders completed a brief demographic questionnaire, the leader version of the Multifactor Leadership Questionnaire, and either the Hogan Personality Inventory or the Hogan Development Survey. Subjects' subordinates completed the rater version of the Multifactor Leadership Questionnaire. Transformational behaviour was operationalised as charisma, which was calculated as the mean of two subordinate rated transformational components of the Multifactor Leadership Questionnaire, viz., idealised behaviour and inspirational motivation. This dependent variable was regressed on the various personality variables to assess predictive ability. Moderation of the prediction of transformational leadership behaviour by personality components was assessed by multiple regression of transformational leadership behaviour on the various personality components within self-subordinate rating agreement categories. There were eight specific original contributions from the findings of this thesis. The HPI component ambition was found to positively predict charisma. The HPI component prudence was found to negatively predict charisma. Self subordinate rating agreement operationalised as an absolute difference score was found to moderate the level of prediction by whole HPI regression model and some of the relationships and predictions of charisma by individual HPI components. It was found that prevalence of personality disorder components among senior executives varied from six percent to 34 percent of the sample cases. The HDS personality disorder components sceptical and cautious were found to negatively predict charisma; whereas the HDS component imaginative was found to positively predict charisma. Self subordinate rating agreement operationalised as a relative difference score was found to moderate the whole HDS regression model and some but not all of the relationships and predictions of charisma by individual HDS components. Theoretical and practical implications of the above findings, limitations of this research and recommendations for future research were discussed.