This thesis describes a research study that investigated associations between teachers' perceptions of principals' interpersonal behaviour and psychosocial environments of secondary schools in Australia. In the past 25 years, much attention has been given to the development and use of instruments to assess the qualities of the classroom and school environment from the perspectives of students and teachers. A new instrument (the Principal Interaction Questionnaire) was developed and validated to measure principals' interpersonal behaviour as perceived by their teachers. The instrument was developed from the Questionnaire on Teacher Interaction. The teachers' perceptions of the school environments are assessed by the well known School Level Environment Questionnaire and copies of both questionnaires were sent to secondary schools throughout Australia where they were completed by the principal and a sample of teachers. Data analysis of the questionnaires showed that there were significant associations between principals' interpersonal behaviour and school environment. For example, there was a positive association between principals' directive behaviour and teachers' perceptions of there being consensus about schools' goals. In addition to the quantitative analysis, a qualitative approach was also used, with the inclusion of interviews from five of the principals who took part in the study.