This study sought to identify important antecedents of principals' self-efficacy (PSE) beliefs among 558 principals in Virginia. Analysis of variance demonstrated that the school context variables of school level, school setting, and the proportion of low-income students had no significant relationship to PSE. Multiple regression revealed that, by and large, demographic variables of gender and race were not strong predictors of PSE. The set of interpersonal support variables at the school-building level (teachers, support staff, students, and parents) was the strongest predictor of PSE, followed by principal preparation and district-level support (interpersonal support from the superintendent and central-office staff, as well as resource support). (Contains 5 tables and 1 footnote.)