Objective: Behavioral inhibition (BI) has been associated with increased risk for developing social anxiety disorder (SAD); however, the degree of risk associated with BI has yet to be systematically examined and quantified. The goal of the present study was to quantify the association between childhood BI and risk for developing SAD. Method: A comprehensive literature search was conducted to identify studies that assessed both BI and SAD. Meta-analyses were performed to estimate the odds ratio (OR) of the association between BI and SAD in children. Results: Seven studies met inclusion criteria. BI was associated with a greater than sevenfold increase in risk for developing SAD (odds ratio = 7.59, p less than 0.00002). This association remained significant even after considering study differences in temperament assessment, control group, parental risk, age at temperament assessment, and age at anxiety diagnosis. Conclusions: Identifying early developmental risk factors is critical for preventing psychiatric illness. Given that 15% of all children show extreme BI, and that almost half of these inhibited children will eventually develop SAD, we propose that BI is one of the largest single risk factors for developing SAD. (Contains 3 figures and 2 tables.)