Hi Mary: I think pop quizes are fine if the students are made aware they can expect a quiz after a lecture. You may find that this helps you fine tune yor lectures, and that's a good thing. Some students take longer to digest fresh material, study their notes, compare notes with textbook, or simply reveiw the material. I have adopted a practice of quiz tomorrow on what we covered today in order to allow students time to grasp all of the material, if possible. That's just my way, other methods may work just as well. Regards, Barry