This article attempted to explicate the process by which laughter is evoked in the interaction with another person. Two experiments were conducted to test hypotheses of the present study. Subjects were college undergraduates, and about equal numbers of men and women participated. The number of laughs, respiration rate, and emotion change were the variables that were examined. Results of Experiment 1 indicated that the mechanism of laughter was related to one of the three dimensions formulated in Wundt's theory of emotion, namely, tension versus relaxation. Results of Experiment 2 suggested that ratings of amusement correlated to some degree with occurrence of abrupt changes in respiration rate. Thus, the two experiments provided some evidence indicating the relation between laughter and the content and process of social interaction. The meaning of the findings and problems of the present study were also discussed.