A major research concern for teacher education is the impact of university credentialing programs on K-12 teaching and the disjuncture between university-promoted practices and what teachers actually do in their classrooms. In particular, mathematics-credential programs typically promote reform-oriented methods, while mathematics teaching in the US remains largely traditional. Proposed explanations for the limited uptake of university-promoted mathematics-teaching methods have included new teachers' struggle to bridge the "two worlds" of the university and school, the relative difficulty of reform-oriented teaching, and the failure of the standard teacher-preparation model that teaches general pedagogical concepts prior to specific teaching tools and practices. In this study, interviews of 19 first- through 4th-year secondary-level mathematics teachers--graduates of a single credential program--investigated the factors, internal and external to the credential program, that these teachers perceived to support or impede their implementation of certain university-taught practices. The findings are used to examine previously proposed explanations for limited uptake, and recommendations are made for credential programs and employing schools.