A classification of structural failures is discussed and then expanded into a set of parameter statements which could be used in a process for predicting the likelihood of future structural failures. The parameter statements are subjectively assessed for 23 major structural accidents and then analysed using fuzzy sets. The failures are ranked in order of “inevitability”. Human errors of one form or another proved to be the dominant reasons for the failures considered. A tentative method for assessing the safety of a structure allowing for the possibility of human error is outlined.