The purpose of this study was to examine how the practicing science and mathematics teachers participating in the University of Florida's Teacher Research Update Experience (TRUE) perceived their experiences in Summer 2000. We conducted in-depth interviews and collected data from survey questionnaires and addressed research in the following areas: How do participants perceive their experiences during the 7-week program designed to enhance science, mathematics, and technology knowledge and skills? How have these experiences contributed to their professional and personal growth and development, and how will they influence teaching and student learning? Findings from interviews provided insights into the thoughts, motivations, and, in some cases, insecurities of these adult learners. Follow-up studies are indicated on long-term impact of immersion professional development programs.