Juan, If I have had the students in a recent class preceding the new one, I have a pretty good idea where students are, in general. If it's been a while, or they're new to me, a review of past information to build a foundation for upcoming topics in my class is helpful. I try to do this in a fun, non-threatening way. What I avoid is statements like "c'mon folks, this is basic information you had back in [insert class]", or "you should know this". Rather, as soon as I sense a majority of students are struggling with information, "whether they should know it or not", I'll pull together some review material, put it into a pre-test, assess results, then determine "OK, this, this, and this needs to have more emphasis. Repitition of past information is never redundant, and I think students appreciate getting a chance to review and reset their thinking for the current class. Barry Westling