Professional development (PD) has been defined as facilitated teaching and learning experiences designed to enhance practitioners' knowledge, skills, and dispositions as well as their capacity to provide high-quality early learning experiences for young children. The purpose of this study was to use a framework from the National Professional Development Center on Inclusion (2008) to characterize key components of early childhood PD by conducting a descriptive systematic review of empirical literature. Two hundred fifty-six studies were identified that met specified inclusion criteria: (a) described a type of PD, (b) involved early childhood practitioners who were working with children birth through the age of 5 years, and (c) reported empirical evidence about PD outcomes for either early childhood practitioners or children. Findings revealed that studies typically included information about PD recipients, the topic or content focus of the PD, and the type of facilitated teaching and learning experiences provided. Seventy-four percent of the reviewed studies included systematic follow-up as a component of the facilitated teaching and learning experiences but limited information was provided about dose and fidelity of implementation of the follow-up. The review provides a descriptive characterization of the who, what, and how of early childhood PD. These data complement an emerging experimental intervention literature focused on second-generation PD research questions. We discuss the need to reach consensus about reporting key components of PD interventions to facilitate interpretations of relationships among PD interventions, improvements in practice, and desired child outcomes.