Social anxiety affects children across the developmental spectrum. Early-onset social phobia may be particularly impairing because of its disruptive effects on social and academic functioning during a child's formative years and because of the elevated risks of childhood adversity in anxious individuals. Unfortunately, little attention has been paid to the early identification and assessment of social anxiety in young children. The ability to recognize and monitor or remediate social anxiety early in development would be of great advantage in reversing this potentially debilitating course. This article reviews various methods available to assess social anxiety and associated conditions. Particular emphasis is placed on the description and assessment of behavioral inhibition in infants and very young children as an early marker or precursor to the development of social anxiety. For school-aged children and adolescents, a greater range of assessment options is available including behavioral observation, clinician ratings, child self-report questionnaires, and parent and peer reports. In an effort to advance our understanding of the developmental psychopathology of social anxiety, further research is necessary to determine the equivalency of various assessment strategies across developmental periods.