Sixty-five fourth-grade, fifth-grade and sixth-grade teachers in the Midwestern United States participated in professional development opportunities designed to increase their mathematics content knowledge and pedagogical knowledge over a two-year series of workshops. Through the use of pre-tests and post-tests assessing content knowledge and pedagogical knowledge, the researchers show that teachers can increase both content and pedagogical knowledge through professional development using grade-appropriate methods. In addition, researchers found that teachers showed positive changes in five areas of beliefs and attitudes, including perceptions of student ability in mathematics. Taken together, these changes indicate a strong potential for changes in classroom practices. (Contains 3 tables.)