This research develops and tests a theoretical model on the impact of antecedents on technology adoption developing valuable insight into influencing levels of attitudes and expectations prior to deployment of a mandated to use system. Two stages during the pre-deployment phase of a mission-critical, mandated system are studied. Results are reported from a two cross-sections field study of 263 and 185 users (physicians, nurses and nurse affiliates) at Critical Care departments of two hospitals implementing a Patient Data Management System. The results indicate that prior to deployment, Trust is the most important predictor of attitudes and expectations. The proposed model explains a relatively large amount of the variance, (64% and 69%) in attitude and (57% and 47%) in expectations before and after training in system use, respectively.