This study reveals possible relationships among teachers' personality traits, situational variables, and deliberation characteristics in planning instruction. Dogmatism and locus of control perceptions were the personality traits studied, and the situations compared student teachers with elementary and secondary school teachers. Both groups were administered dogmatism and locus of control measurement scales, and were asked to "think aloud" in a process of simulated planning of instruction. Detailed written protocols of the "think aloud" process were analyzed and rated in view of characteristics derived from measuring levels of dogmatism and locus of control. Findings indicate: (1) Significant differences exist between student teachers and teachers at both the elementary and secondary levels; and (2) Dogmatism and locus of control perceptions explain variances in teachers' deliberations. Interpretations and possible implications for teacher education are put forward. (Author/FG)