In order to understand psychiatric factors that complicate the medical management of somatizing patients, 94 subjects with known somatization disorder (SD) were evaluated for 13 personality disorders with the Structured Clinical Interview for DSM-III-R Personality Disorders. Referred from multiple primary care settings, the patient sample was predominantly female (85%), married (67%), high school graduates (64%), and had a mean age of 43. Structured interviews documented that 23.4% of SD patients had one personality disorder, and 37.2% had two or more disorders. The four most frequently identified personality disorders were avoidance 26.7%, paranoia 21.3%, self-defeating 19.1%, and obsessive-compulsive 17.1%. Interestingly histrionic personality disorder was identified in only 12.8% of the sample and antisocial personality disorder in 7.4%. In making the diagnosis of SD, health care providers need to avoid the common clinical impression that histrionic behavior often accompanies the disorder. Further research with SD patients is needed to examine the relationship of co-occurring personality disorders to symptom recurrence, health care utilization, and readiness for psychiatric referral.