In recent years, different researchers and research agencies, teacher associations, national education organizations, and the U.S. Department of Education have published lists of the characteristics of effective professional development to guide school leaders in their improvement efforts. This study analyzed 13 of the better known of these lists to determine whether they were derived through similar procedures, based on similar frames of reference, and included the same elements or characteristics. Results show that individual characteristics vary widely in their frequency of inclusion in the lists and that no characteristic is consistently named in all lists. In addition, research evidence supporting most of the identified characteristics is inconsistent and often contradictory. Implications for leaders interested in improving professional development activities are discussed, as well as ways to enhance efforts to identify the characteristics of effective professional development.