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." This study analyzed 13 of the better known of these lists to determine if they were derived through similar procedures, based on similar frames of reference, and included the same elements or characteristics. Results showed that individual characteristics vary widely in their frequency of inclusion on 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 improving the quality and effectiveness of professional development are discussed. (Contains 56 references.) (Author/SM)