From Princeton Review's Web site:
All applicants are sent secondary applications. Between 400 and 500 applicants are interviewed from September through February. These candidates are selected from a pool of about 2,000, meaning that about 20 percent of applicants make it to the interview stage. Interviews consist of two sessions each with a faculty member or medical student. On interview day, there are also group informational sessions, a campus tour, and the opportunity to have lunch with current medical students. The first acceptance letters are mailed in October, with subsequent batches of letters sent at 4-6-week intervals throughout the year. Approximately 30 percent of interviewees are accepted initially. Others are rejected or placed on a wait-list. Supplementary material from wait-listed candidates is not encouraged. Usually 60-70 percent of interviewees are eventually offered an acceptance before orientation begins.