Behaviors of organizational members can be classified as two types. One is behavior required to perform formally given job. The other is a various kind of behavior taken voluntarily but not required directly and formally to perform job. The former can be called as in-job behavior while the latter can be called as extra-job behavior. Many organizational scientists so far, have focused on investigating in-job behavior. Yet, from a decade, organizational researchers have recognized that in-job behavior alone can not explain sufficiently job performance or organizational effectiveness Thus. they have paid attention to extra-job behavior, which is generally called as organizational citizenship behavior. Existing studies of organizational citizenship behavior have three types : First type is studying the concept and components of organizational citizenship behavior. Second tope is studying the determinants of organizational citizen-ship behavior and relationships with it. And third type is studying relatioships between organizational citizenship behavior and job performance. This study, therefore, have purposes as follows : Firstly, this study designs a comprehensive model in the below figure and generates inclusive hypotheses about relationships among antecedents, intermediate factors, and the components of organizational citizenship behavior. Secondly, this study investigating empirically such relationships and draws a picture of mediation roles of the intermediate variables. To design the model and generate the hypotheses, this study conducted a comprehensive literature survey on organizational citizenship behavior. To test the hypotheses, this study collected data from 847 employees at 12 large genral hospitals in Pusan area through a questionnaire survey and conducted the three step mediated regression analysis using the SAS-PC Package.