This chapter looks at the various limits on the effectiveness of humanitarian action in armed conflict and disaster. While the big picture of international humanitarian action is very positive and shows a significant growth in humanitarian finance and coverage in recent years, every humanitarian operation still has to deal with a range of barriers that routinely block total humanitarian success. These barriers are identified as political; organizational; technical; communal; and moral. All barriers combine to different degrees in every international humanitarian operation to reject, skew, confuse, and inhibit humanitarian action. As perennial problems, these difficulties are the natural operating environment for any humanitarian worker. Introducing humanitarian action into armed conflict and disaster will always be a negotiated struggle that is dependent on ideologies, systems, and behavior which are regularly beyond the direct control of medical humanitarian agencies.