Teacher preparation programs invest significant resources to influence the beliefs of preservice teachers, including clinical faculty who mentor preservice teachers during practicum experiences. Despite the work of university personnel to guide preservice teachers' beliefs, their influence wanes once preservice teachers cross the threshold into inservice teaching. New mentors, including mentor teachers, instructional coaches, and administrators take the place of university personnel. This quantitative study examined how the beliefs of 77 novice inservice teachers changed toward reform-based mathematics instruction during their first year of teaching. Of the 77 subjects, 50 were interns and 27 had completed student teaching. Near the end of their first year of teaching, subjects were surveyed for their current beliefs at the time of completing the survey. Their beliefs from the time immediately preceding the beginning of their first year of teaching were measured retrospectively. During their first year, school-based personnel served as their "˜transitional faculty' as they supported the novice teachers' teaching experiences. The novice inservice teachers' perceptions of the transitional faculty's beliefs and support, as well as the alignment of their curriculum materials, were also surveyed. Relationships between changes in the beliefs of the novice inservice teachers and their perceptions of their transitional faculty and curriculum were examined. The overall belief means for novice inservice teachers decreased, the extent of which is statistically significant. Analyses of covariance revealed that the perceived beliefs and support of transitional faculty played a statistically significant role in the belief change of novice inservice teachers, as did their curriculum materials. This study highlights the importance of creating systems to improve mentor selection and training so the work of university personnel is not undone during the novice's first year of teaching.