The purpose of this study was to analyze the process by which an innovative running program was disseminated through certain channels along time process among the runners. At the same time, it was also aimed to illustrate the applicability of the diffusion research method in sport situations. Data were collected from 2,616 persons who took part in the pop marathon race held in Fukui, Japan, by means of mailed questionnaires in the fall of 1983. Concerning innovativeness and opinion leadership of the pop marathoners, findings supported some of Rogers' generalizations as follows: 1) Earlier participants/adopters have a higher degree of opinion leadership than later participants/adopters. 2) Individuals tend to be linked to others who are close to them in participant/adopter categories. And, when interpersonal diffusion networds are heterophilous, followers seek opinion leaders who are more innovative. 3) Mass media channels are relatively more important than interpersonal channels for earlier participants/adopters than for later participants/adopters. 4) Later participants/adopters are more likely to discontinue running as a sport innovation than earlier participants/adopters. 5) Opinion leaders are more cosmopolite than their followers.