Diverse as HROs may seem, we lump them together because they all operate in an unforgiving social and political environment, an environment rich with the potential for error, where the scale of consequences precludes learning through experimentation, and where to avoid failures in the face of shifting sources of vulnerability, complex processes are used to manage complex technology (Rochlin, 1993).

We will argue that HROs are important because they provide a window on a distinctive set of pro-cesses that foster effectiveness under trying conditions.The processes found in the best HROs provide the cognitive infrastructure that enables simultaneous adaptive learning and reliable performance.

We then move to the heart of the analysis and argue that organizing for high reliability in the more effective HROs, is characterized by a preoccupation with failure, reluctance to simplify interpretations, sensitivity to operations, commitment to resilience, and underspecifi ed structuring. These processes reduce the inertial blind spots that allow failures to cumulate and produce catastrophic outcomes.