The determinants of teacher burnout were investigated in a sample of secondary school teachers in Cyprus. Using a bunch of self-respond instruments a total 319 teachers all over the island responded to scales that assessed various aspects of organizational and personal characteristics of burnout. The Maslach Burnout Inventory was used to assess the level of burnout as indicated by its three facets: emotional exhaustion, depersonalization and personal accomplishment. An hypothesized model was tested using structural equation modeling techniques. The causal model examined the linkages that exist among organizational (professional demands and responsibility, student misbehaviour, time pressure, pupil’s abilities and attitudes to work, professional status, school rules, school inspectorate) as well as personal – internal characteristics (professional efficacy, self-esteem) and vocational teacher stress. Implications of findings for the development of research on educational effectiveness research are drawn. Emphasis is given to the importance of investigating the impact of teacher burnout upon school effectiveness.