Studies have found teachers' participation in professional development (PD) is associated with higher-quality interactions between teachers and children in their classroom, and with improved academic and social-emotional outcomes for children. Based on these findings, Head Start has made important investments to provide high-quality PD to their teachers, requiring teachers to attend at least 15 hours of PD every year. The purpose of this study is to improve our understanding of PD in Head Start by investigating if there are meaningful patterns, or constellations, of PD supports experienced by a national sample of Head Start teachers, and if teachers' experience of PD supports is related to teachers' practice and children's academic and socio-emotional outcomes.