I had 2 first-round interviews on campus, both of which were case interviews. 3 second-round interviews were then held in the San Francisco office. The structure of all the interviews was very similar, with the first 5-10 minutes being resume-based. The questions here were pretty standard and generally nothing to worry too much about. The next 25-30 minutes are dedicated to the case portion of the interview. BCG has a very analytical culture, so be prepared to work with numbers throughout the case. Finally, the last 10 minutes or so are reserved for questions. This part is also pretty standard, although it can be a good time to gain a few bonus points if you can ask poignant, thought-provoking questions. I had a great experience with all five of my interviewers, with all of them being very open and helpful. In general, it is very important to make the case into a dialogue with the interviewer, rather than a presentation or solo exercise. Although most of the interviews I had were partners at the firm, they were very willing to help work through the case and add helpful insights along the way.