Although many studies have focused on the effects of social desirability in personality measures, few have analysed its effects on such highly undesirable behaviour as aggressiveness. The present study analyzes the impact of social desirability on measures of direct and indirect aggression and on the relationships between both kinds of aggression with impulsivity, using a method that enables the content factors of the measures to be isolated from social desirability. Results showed that aggression measures are highly affected by social desirability and that the relationships between the two forms of aggression and impulsivity are due to the content measured by the tests and not to a common social desirability factor.