The objective of this study was to determine the co-occurrence of 7 of the 10 Diagnosis and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision ( DSM-IV-TR ) personality disorders (PDs) in the US population. Face-to-face interviews were conducted with 43 093 respondents in the National Institute on Alcohol Abuse and Alcoholism's 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions, a nationally representative survey of the US population. Odds ratios were calculated to determine associations among PDs. All associations among PDs were positive and statistically significant. PDs were significantly associated with other PDs within the same cluster, in addition to being highly associated with PDs of other DSM-IV PD clusters. Co-occurrence between DSM-IV PDs is pervasive in the US general population. Future research is needed on the creation of dimensional representations of DSM-IV PDs as an adjunct to categorical diagnoses.