The potential of ERP systems cannot be fully realized unless adopting firms make a concerted effort of assimilating the ERP technology into every aspect of their business processes.Yet few studies provide understanding of why ERP assimilates more extensively in certain organizations as against others (post-adoption).Based on the extant literature, we propose a model which can be employed to explain the extent of ERP assimilation.The model incorporates top management championship, compatibility, institutional influence, and absorptive capacity factors.This paper describes the model development, the model testing, and some preliminary results.