Background: Residents' perceptions about evidence-based clinical decision making remain largely unexplored. Purpose: To understand how residents perceive and use evidence-based medicine in clinical decision making. Methods: Qualitative study using a semistructured questionnaire and focus group in a postgraduate training program in internal medicine at an academic U.S. medical center. Seventeen 1st-year internal medicine residents in their 1st postgraduate year were interviewed. Six additional 1st-year residents formed a validation group. Results: The interplay of time and expertise modified how physicians-in-training incorporate evidence into clinical decision making. When time was available, the residents preferred to answer their questions by searching and critically appraising the literature. This "self-acquired" expertise empowered them to help patients by using participatory decision-making styles. When time was limited, the residents turned to experts. Residents assumed that experts practiced evidence-based medicine. This "borrowed" expertise was thought to be the most efficient way of integrating evidence and clinical expertise, but it led to the use of a parental style when answers were taken back to the bedside. Conclusion: The practice of evidence-based medicine empowers 1st-year residents and appears to affect their choice of decision-making style. Further research is needed to better understand the link between decision-making style and evidence-based medicine.