This research tested some of the basic structural assumptions of Jeffrey Gray′s personality theory and the potential applicability of this model to the anxious-fearful and erratic-dramatic Diagnostic and Statistical Manual of Mental Disorders - Third Edition, Revised (DSM-III-R) personality disorders. Two independent samples, a normative sample (477 college undergraduates) and a research sample (77 persons, two-thirds with at least one personality disorder), were employed. Findings from both samples provided converging support for the hypothesized location of Gray′s primary personality dimensions. More importantly, additional analyses based on the research sample indicated that the dimension of anxiety underlies personaliy disorders included in the anxious-fearful cluster and that the dimension of impulsivity underlies the disorders of the erratic-dramatic cluster, suggesting that Gray′s primary dimensions of personality constitute one viable model for conceptualizing two clusters of DSM-III-R personality disorders.