McKinsey came out with an initial shortlist on the basis of our resumes. The next step was a logic test that ran for about 45minutes to an hour. The scores are kept handy by the interviewers on the day of the final interviews. I had 5 rounds of interviews on the day. 3 of them were case interviews, whereas 2 were either CV based or based on personal questions. In the case interviews, the emphasis was on checking the candidates problem solving skills (quantitative / logic skills) as well as structuring of the problem. The personal interviews laid stress on the communication skills and thought clarity of the interviewee. Very important to be crisp in your responses and take time out to think before you speak. Writing down notes in a legible and clean handwriting is again very helpful. Pretty friendly firm culture during the interview, and in the office as well.