A cohort of 2,171 substance abusers were assessed for their gambling behavior, and divided into three groups: those with no significant gambling problem (87%); those with a probable problem (7.2%); and those with a severe problem (5.8%). Substance abusers with a gambling problem scored significantly higher on measures of: impulsivity; disinhibition of aggressive/hostile responses; and negative affectivity. They also abused more substances than the nongamblers. The results underscore the importance of assessing a wide range of impulsive behaviors in substance abusers and the potential for subtyping substance abusers based on psychological traits.