This paper reports on a study conducted on the National Assessment of Educational Progress (NAEP) 2005 database. The purpose of the study was to examine predictors of student achievement using middle school mathematics teacher professional development items as criterion variables, such as the number of mathematics courses taken, the number of mathematics education courses taken and professional development in various pedagogical strategies. A multiple regression analysis was conducted on the eighth grade database. The results indicated that a statistically significant association was found between the number of mathematics courses taken and student achievement, and that the number of mathematics education courses was not associated with student achievement. Moreover, a statistically significant association was found for the amount of professional development where students of teachers who reported receiving a small amount of professional development tended to have higher achievement. The relationships for other professional development activities are also reported. Recommendations include that middle school mathematics teachers should receive a small extent to a moderate extent of professional development with the areas of mathematical theory and applications of mathematics, content standards, the use of curriculum materials, the use of calculators for developing mathematical concepts and strategies for assessing student learning. (Contains 3 tables.)