Mentoring is believed to be one of the most influential factors in US efforts to encourage college-aged students to seek careers in science, yet the role that mentoring plays in this process has not been elucidated. The researchers were interested in understanding whether the long-held beliefs about the importance of mentoring would be revealed as what actually occurs in an undergraduate research program. They describe students' perceptions of the mentoring process and students' beliefs about how it impacted their experiences as undergraduate researchers and their development as scientists. Also described are professors' perceptions of their roles and effectiveness as mentors in students' development as scientists. A multi-case narrative analysis was conducted of two groups, undergraduate science scholars (n = 5) and mentoring professors (n = 5), who were each interviewed on two occasions at the beginning and end of the first year of a funded research program. As this grounded research study shows, students and professors described student gains as increased technical expertise and communication skills. Professors suggested that they were available to students on a regular and frequent basis. However, students' experiences suggested a contradiction. They were often mentored by postgraduates, technical assistants, and other students; their meetings with mentoring professors were infrequent and at times distant. With respect to mentoring, this finding highlights the differences between beliefs and the reality of what was delivered. Professors discussed the challenges associated with mentoring including the recruitment of and difficulty of working with students whose first language was not English and concerns about the quality of instruction from graduate students. (Contains 5 tables and 1 figure.)