This quantitative study investigated the relationship between teacher dispositions, subject content knowledge, pedagogical content knowledge, and reasons that school principals recommend non-renewal of probationary teachers' contracts. Principals in the Southeastern Unites States completed an e-mailed survey. Two nonparametric tests, Kruskal-Wallis and Mann Whitney U, were used to statistically analyze group responses. Principals reported that they observed most a lack of pedagogical content knowledge from ineffective teachers and they prioritized the importance of instructional skills in deciding whether to non-renew a teacher contract. Principals identified teacher integrity, dependability, and honesty as important dispositions. The studies' findings are important for universities that prepare preservice teachers and also for the planning of professional development initiatives. The study findings suggest that principals tend to view dispositions as personality characteristics rather than as teacher competencies and that teacher expertise in both subject content and pedagogy must be woven together. (Contains 3 tables.)