The concepts of credibility, attraction, power, and "homophily" (degree to which source and receiver are similar in certain attributes) have been investigated as independent and unrelated variables in the communication process. The authors seek to establish the relationship of these variables as subdivisions of the overriding concept known as source valence. First, they establish the theoretical foundations of the four components. Second, they summarize previous research on the components and then set goals for future research. Third, the authors examine some of the problems of the research methodology in this area. Their final suggestion is that researchers concentrate more on source valence rather than the subsets. (Author/RN)