Tranmer, M., Pallotti, F., and Lomi, A. (2016) The embeddedness of organizational performance: multiple membership multiple classification models for the analysis of multilevel networks. Social Networks, 44, There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/122367/ hospitals (higher-level, elective transfers), and between EDs and hospitals (cross-level, nonemergency transfers). Our main analytical objective is to examine the effect of these interdependent and partially nested levels of action on the variation in waiting time among EDsone of the most commonly adopted and accepted measures of ED performance. After controlling for institutional and organizational differences between hospitals, we find that the largest component of network variation in patient waiting-time is accounted for at the level of the hospital-to-hospital patient transfers. We take this result as clear evidence of the presence of multilevel network effects on organizational sub-unit performance. We also find that EDs connected by direct patient transfer relations tend to attain similar levels of performance. We interpret this performance spillover effect as evidence that collaborative network relations afford and sustain processes of interorganizational learning and knowledge transfer at the sub-unit level. We discuss further extensions to the model for more general analyses of multilevel network dependencies.