This study investigated the impact of a district-wide mathematics professional development program on elementary teachers' general and personal efficacy. It also explored connections among teacher efficacy and socioeconomic status with student achievement. Using a quantitative approach, a job-embedded professional development initiative sustained over a 2-year period with 35 teachers was found to increase teachers' general and personal efficacy in teaching mathematics. The investigation of the professional development work was based on the principles of effective mathematics professional development, efficacy theory, and student achievement. To measure perceptions of teachers' general and personal efficacy, teachers of third graders in 10 Kentucky elementary schools were asked to complete the Math Teaching Efficacy Instrument (Enochs & Riggs, 1990) version of the Teacher Efficacy Scale (Gibson & Dembo, 1984). Of the 40 original participants, 35 returned usable surveys for a return rate of 88%. The measure of student achievement for this study was mathematics scores derived solely from the performance of third graders on Kentucky's state-mandated Kentucky Core Content Test for mathematics. Teachers' general and personal efficacy was measured using a paired-samples "t" test. The "t" test revealed a significant difference in teachers' general and personal efficacy before and after the professional development program. Student achievement was regressed over the measures of teachers' general efficacy, teachers' personal efficacy, and socioeconomic status (lunch status). This regression model yielded general efficacy and socioeconomic status as significant predictors of student achievement. In addition, it was determined that a relationship exists between teachers' general efficacy and student socioeconomic status with student achievement in mathematics. Although the study did not find that teachers' personal efficacy was a significant predictor of student achievement, an indirect relationship could be implied because personal efficacy was correlated with general efficacy. Thus, the researcher concluded that job-embedded, sustained professional development indirectly leads to improved student achievement in mathematics. This finding was true even when socioeconomic status was taken into account. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]