One of the biggest challenges for instruction in large-enrollment introductory courses is identifying points of student confusion. One technique that is used to address this problem is the muddiest-point card. However, this technique is logistically difficult to implement in large classes. Personal response devices (or clickers) can be used to facilitate this technique. Instead of providing students a blank card, students are asked to identify their "muddiest point" from an instructor-provided list of topics covered in that day's class. The use of clickers allows students to maintain the anonymity normally associated with the cards used in the traditional implementation. Incorporation of muddiest-point questions into the first and second terms of a general chemistry course is described. About three-quarters of the students who answered other clicker questions during class also answered the muddiest-point clicker question at the end of class. While approximately 75% of the muddiest-point topics were conceptual in nature, quantitative topics were more likely to be chosen as the muddiest point. (Contains 3 figures.)