The use of humor in teaching has been linked to learning in several studies, although the research has been equivocal. The various types of humor used by teachers have also been investigated but not in terms of what students view as appropriate and inappropriate uses of humor. Participants in this study were asked to generate examples of appropriate and inappropriate uses of humor by teachers. Responses were unitized and content analyzed, resulting in the identification of four appropriate humor categories and four inappropriate humor categories. Each category is defined, and the implications of using different types of humor in the classroom are discussed. (Contains 4 tables.)