The present study seeks to replicate and expand findings from earlier studies that pathological gamblers manifest elevated traits of impulsivity. Secondly, the study aims to elucidate the relationship between impulsivity, indices reflecting severity of pathological gambling and other measures of psychopathology and personality dysfunction. Case series. Eighty-two consecutive gamblers, seeking treatment for problem gambling. Impulse Disorders Research Unit, School of Psychiatry, University of New South Wales, Australia. Semi-structured interview designed to obtain demographic information and gambling history, the South Oaks gambling Screen, the Eysenck Impulsivity Scale, the Personality Disorder Questionnaire-Revised, the Beck Depression Inventory and the Beck Anxiety Inventory. Results show elevated traits of impulsivity among clinic samples of pathological gamblers compared to normative data and show that impulsivity is related to the severity of gambling behaviour as measured by the South Oaks Gambling Questionnaire. A principal component analysis of the Eysenck Impulsivity Scale and the personality Disorder Questionnaire-Revised, demonstrated that the concept of the "antisocial-impulivist" identified to Blaszczynski, Steel & McConaghy (1997) is not only characterized by impulsivity and antisocial personality disorder but also by high loadings from other cluster B and cluster C personality disorders. CONCLUSION. This research supports the role of the construct of impulsivity in mediating the severity of gambling behaviour and associated behavioural and psychological disturbance among pathological gamblers presenting for treatment. Impulsivity is best understood as part of a general personality disorder structure characterized primarily by DSM-III-R Axis II cluster B and some cluster C personality disorder.