The sustainability of improved pedagogy gained through professional development (PD) of mathematics teachers has undergone little empirical study. In a midsized urban school district in the Northeastern United States, all high school mathematics teachers attended a 3-year mandatory PD program. Although an external evaluator studied this program immediately after completion, there had been no longitudinal study of the perceptions of its participants regarding the sustained benefits of the program. This qualitative study offered a follow-up study of the participants in the Math and Science Partnership (MSP) PD program to provide insight to administrators regarding the sustainability of benefits gained through the MSP program. The conceptual framework for the study consisted of Desimone's model for evaluating PD and Kleining's framework of systematic exploration and inquiry. The participants (N =7) were asked about their perceptions of the value, applicability, longevity, and efficacy of their MSP PD and their suggestions to improve the program. Data were organized and analyzed using Patton's semistructured systematic framework to reveal general consensus as well as anecdotal evidence. The perceptions of the mathematics teachers provided pertinent information that administrators could use to determine the format of future PD. Teachers participating in this study indicated that having a college professor present a combination of content knowledge and pedagogy skills made the MSP program highly effective and long-lasting. Using this feedback, district leaders could institute improved PD, giving their teachers the skill and knowledge to lift their students academically. Closing the mathematics achievement gap may open employment and college opportunities to students which allow them to escape poverty and lead more successful lives.