I am referring to the basic science ones (pharm, physiology, behavioral, biochem, etc). How similar are the questions to the USMLE Step 1, and are the questions as difficult? I know the USMLE has two-step and three-step problems, do these questions show up on the shelf exams also? I'm a little confused because I understand these are third-year tests and the USMLE is taken at the end of the second year. I also read in an earlier post that the shelf tests are more knowledge/achievement and the USMLE is more integration/application. Is that correct?