Examination of a number of major studies of personality questionnaires reveals the existence of a shyness factor which is related to but separable from both introversion and neuroticism, and which loads on items referring to feeling uncomfortable and self-conscious, and keeping in the background in certain kinds of social situations. The fears that are generally expressed about social situations--of being negatively evaluated and of being socially inadequate--are reflected in subjects' descriptions of the causes of shyness, and these findings suggest a model of shyness in terms of individual differences in susceptibility to threat.