High profile documents in early childhood education describe Intentional Teaching (IT), yet little research has been undertaken to give specificity to the definition so that application is possible, for example, to determine and prioritize information to include in professional development, assess fidelity of the implementation of that professional development, and measure impact on teachers. Prekindergarten teachers in a community-based Head Start program participated in the study and were observed during large-group and centers/small-group activities. Three studies using mixed methods are presented. In 2 of the studies, experts together observed focus teachers with attention to coding all instances of IT. They then discussed their observations. Discussions were recorded and analyzed with grounded theory analyses. Features of IT were specified. The additional study used direct observations of teachers to assess their IT, comparing those given professional development centered on IT and a control group. Findings from the studies enriched and refined our understanding of IT and provided necessary features of IT. Application of the findings is provided. (Contains 3 tables.)