The Mathematical and Theoretical Biology Institute (MTBI) was founded in 1997 at Cornell University and is currently housed at Arizona State University (ASU). MTBI’s main objective is to increase the representation of U.S. underrepresented minority students in the U.S. earning Ph.D.s in the mathematical sciences. MTBI focuses on a pool of participants primarily composed of students from “nonselective” institutions and students who typically do not consider the possibility of graduate school in the mathematical sciences. Over the course of 15 summers, participants have generated 146 technical reports and a large number of refereed publications while having a direct impact on the research programs of ASU’s graduate students, postdoctoral fellows, visiting professors, and regular faculty. MTBI has enrolled a total of 328 first-time undergraduate students and 69 returning students in its summer program. Over this timeframe an additional 114 graduate mentors have participated. Sixty-eight participants to date have earned Ph.D.s.