The 520 million year evolutionary history of the Cephalopoda is punctuated by a number of severe crises during each of which this class came very close to extinction. These are fully documented only for the externally shelled, or ectocochlian, cephalopods to which my remarks are, therefore, restricted. The word crisis should be defined narrowly in the sense in which it is used in medicine, business, and the social sciences: “a condition…. felt to endanger the continuity of the individual or his group “(Webster's Third International Dictionary). Within species, genus, and family groups evolutionary crises are, of course, commonplace, and even orders may disappear without threatening the extinction of an entire class. It is only when all, or almost all, taxa of family-group and lower hierarchic level disappear more or less simultaneously, or within a geologically very short period of time, that we may speak of a crisis, a situation that threatens the very survival of a class, or higher taxon, of organisms. It is the purpose of this presentation to study in some detail this kind of situation as it has affected the evolutionary history of the Cephalopoda.