Humor is an important tool for the teacher in college classrooms. Generally, laughter is a great benefit in anyone's life, having even physiological influence. Laughter reduces stress and may facilitate creativity. However, the use of humor can both enhance and hinder the learning process. Various researchers have tried to identify structures, types, and categories of humor. Humor in the classroom setting is undesirable if a student is the target of the joke. On the other hand, when care is taken by the instructor to avoid negative consequences, humor has been shown to have a positive effect in the classroom. The gender of the participants in the humorous transaction may dramatically influence the outcome of the situation. Also, there are significant differences in how the genders react to humor. Overall, the frequency and use of humor correlates positively to perceived appeal, effectiveness, and delivery, but for male instructors only. Instructors can encourage laughing at humorous circumstances to build a feeling of unity in the classroom. They can also use humorous examples or present concepts humorously to help students comprehend and retain lecture material. Effective instructors must bring a full range of resources into today's classroom, and one of these resources, used moderately and appropriately, is laughter. Fifteen principles for using humor in the college classroom are included to provide guidance for college instructions. (Thirty-seven references are attached.) (HB)