Professional development (PD) for early childhood educators has received increased attention as a means of bolstering young children's learning and development. Theory and research indicate that educators' characteristics play roles in both their own learning and that of children; however, little research has explored who participates in PD. This study provides an in-depth description of the backgrounds and qualifications, positions and settings, knowledge, and beliefs of educators participating in PD offerings. These educator characteristics have been identified as important factors in adult learning theory with implications for the design, implementation, and evaluation of adult learning. Descriptive analysis revealed considerable variability in many of these characteristics. Findings yield practical implications for the design of future large-scale PD efforts in terms of format, content, and marketing. (author abstract)