RESUMO
1) We conducted a randomized controlled trial in medical education area and explored practical issues through reflection on the processes.<br>2) In February 2007, 39 fourth-year medical students in Nippon Medical School listened to the lecture about how to ask key questions for the diagnosis. Shortly after they had medical interview with a standardized patient for measurement purpose. They were randomly allocated to study and control groups. The lecture content for the intervention group corresponded to the interview but the one for the control group did not correspond to the interview.<br>3) We identified the issues related with ethical review for research, how to mask the information of randomization out of assessors, and equity of educational intervention and assessment offered to both groups.