This article is based on the findings of a 2-year study that examined the nature of effective faculty/student undergraduate research (UR) science, technology, engineering, and mathematics (STEM) relationships. The study site was a large urban public college where three fourths of all incoming freshmen receive need-based aid; and although not a historically Black college or university (HBCU), 85% are students of color. The college offers 2- and 4-year STEM degree programs. Utilizing cultural historical activity theory (CHAT) as both a theoretical and methodological framework, this phenomenological study employed semistructured interviews, written surveys, and member checking to understand four paired faculty/student UR mentoring relationships over 2 years. The findings not only concur with the bulk of UR research, indicating UR's promise for addressing the low enrollment and retention rates of students of color in the STEM disciplines but also raise issues around the emotional, financial, and professional costs to UR faculty. It is these costs that are the focus of this article that concludes with ideas, for university and college administrators and all others concerned, about on how we might support faculty in UR's crucial work toward the goal of retaining students of color in STEM. © 2012 Wiley Periodicals, Inc. Sci Ed 96:527–542, 2012