Drawing on an inquiry into Israel's preparedness for biological threats, in this article I suggest a new analysis of biosecurity events. A complex and dynamic assemblage emerges to prepare for biological threats, one that I call a "pre-event configuration." The assemblage is composed of three core elements-the scientific element, the security element, and the public health element-each of which diagnoses threats and suggests appropriate solutions. This configuration also determines what will be perceived as an event for which preparation is needed and what will remain a nonevent. I maintain that the constitution of an event takes place beyond the actual time of its occurrence and is determined by the pre-event configuration in the "time of event." Therefore, a comprehensive analysis of events should combine an examination of actual events and their aftermath with an inquiry into their potentialities as determined by the pre-event configuration. [biosecurity, preparedness, events,disasters].