Background: The primary objective of this study was to prospectively examine the role of Avoidant Personality Disorder (AvPD) as a determinant in the outcome of Generalized Social Anxiety Disorder (GSAD) using Wave 2 of the National Epidemiologic Survey of Alcohol and Related Conditions 3 years later. Method: This study analyzed data from Waves 1 and 2 of the NESARC (n = 34,653). GSAD was operationalized based on the DSM-IV definitions of this SAD subtype. Results: Logistic regression analyses indicated that AvPD significantly predicted the persistence of GSAD, even after adjusting for a number of important sociodemographic variables and other psychiatric comorbidity. AvPD did not significantly predict outcome in non-generalized SAD. Conclusions: AvPD can influence the course of GSAD in adulthood. Specific personality dimensions may underlie and explain the similarities between AvPD and GSAD. Self-criticism could be a shared feature of both AvPD and GSAD and could represent an important psychological marker of poor prognosis in comorbid GSAD and AvPD. Depression and Anxiety 28:250–255, 2011. © 2011 Wiley-Liss, Inc.