The herd behavior of technology users, i.e., adopters observe the decisions (but not the reasoning) of prior adopters and imitate their system usage behaviors, is prominentin the information technology (IT) industry. However, such en mass adoptions areprone to be fragile. Adopters may reverse their decisions, after an initial adoption, andabandon system use when updated contradictory information is presented. This phenomenon of herd-like abandonment, at both individual and organizational levels, is significant and requires more investigation, since it is connected to the durability of particular products and technologies in the marketplace. In addition, IS behaviors of users at the later phases of IS life cycle, i.e., termination phase, are the primary source of benefit for organizations. This study develops and empirically validates a theoretical model of IS abandonment in a herding context. We test our model via a longitudinal research design, which surveys adopters at two different points in time. The study examines the determinants of adopters' abandonment intentions, which occure specially after an initial en mass adoption (i.e., a herding setting). Results suggest that post-adoptive task-technology fit, perceptions of niche, and observation of a criticalmass of abandoners are all salient factors affecting IS abandonment intentions.