Objective: The purpose of the study was to determine the prevalence of personality disorders among a large population of persons seeking treatment in a public psychiatric facility and to examine the role of personality disorders in the clinical conditions of persons frequenting such facilities. Methods: Clinical and demographic data were retrospectively examined for 18,179 adults who visited a walk-in clinic of a public psychiatric facility between 1983 and 1989. Patients who received a diagnosis of personality disorder were compared with those who did not. Results: A total of 2,344 patients (12.9 percent) were diagnosed as having a personality disorder, a lower prevalence rate than generally found in treatment populations. The most frequent diagnoses were atypical, antisocial, and borderline personality disorders. Compared with other subjects, those with a personality disorder were significantly more likely to be men, to be 35 years old or younger, to have a higher level of social impairment, and to have more symptoms and more severe symptoms. Conclusions: The relatively low prevalence rate was attributed in part to underdiagnosis, largely due to the need for making rapid assessments in a public intake setting. The authors conclude that clinicians in such facilities may be likely to diagnose personality disorders when patients with certain axis I disorders such as substance use, affective and adjustment disorders present with an overall greater level of symptomatology and social impairment.