Profile analyses were used to investigate differences in the self-efficacy growth of teachers with more and less mathematics background as the teachers participated in professional development across two summers. Professional development activities were associated with increases in teachers' self-efficacy; however, without considering mathematics knowledge for teaching, teachers with more math background tended to benefit more than those with less background. Nonetheless, teachers with less math background had higher levels of teacher self-efficacy although this gap was closed by the last measurement. Such considerations are important when designing professional development as teachers may have different needs based on specific characteristics such as preparation in their teaching domain. (Contains 3 tables and 4 figures.)