Decades of research on the study of introversion and extraversion have allowed researchers to distinguish among individual differences on each of these dimensions. Research indicates that shyness, a rather common personality trait, is a construct that is related, but not identical, to introversion. Once regarded as a unitary construct, modern day personality theorists propose that shyness is based on a number of orthogonal dimensions. Empirical evidence suggests that distinct subtypes of shyness develop as a result of differences in social approach and social avoidance behaviors. Temperamental shyness is a risk factor for behavioral and affective problems, as well as more severe psychological problems. This article focuses on the phenomenon of shyness by reviewing its subtypes, psychosocial correlates, and efficacious treatment interventions.