Ongoing educational reform initiatives have ushered in significant changes in teacher-certification regulations. Many states no longer offer permanent certification, but instead require teachers to participate in career-long professional development (PD). Accordingly, increasing attention is being paid to the effectiveness of PD initiatives, raising questions concerning how best to provide PD services for teachers--e.g., how such services should be designed, what topics they should cover, and which teachers should be served. Studies indicate that PD initiatives varied in effectiveness depending on their design features. However, the success of these initiatives likely depends as well on the characteristics of the teachers who take part in them. This paper reports the results of a study that examines how the following characteristics--age, years of teaching experience, gender, grade level (elementary versus secondary), and level of educational attainment--are associated with teachers' attitudes about PD. (Contains 3 tables.)