Reboxetine is a novel antidepressant with a selective action on noradrenaline. In addition to its efficacy in depression, it has been found to improve social adaptation. The objective of this study was to assess the specific social behavioural effects of reboxetine which might be associated with social adaptation. Ten pairs of healthy volunteers took part in a randomized double-blind, crossover study of 2 weeks treatment with reboxetine (4 mg b.d.) and placebo with a 2-week washout period. In each pair, one person (subject) took the tablets and the other (flatmate) received no treatment. On the last day of each treatment period, the subjects socially interacted with a stranger (a confederate behaving as a responsive person) in a stranger-dyadic social interaction paradigm. After the interaction, subjects played the Mixed-Motive game, which measures cooperative behaviour and communication, with the confederate. Subjects read a short story before and after the social interaction. The flatmates evaluated the social behaviour of the subjects before and at the end of the two treatment periods. On reboxetine, the subjects were rated to be significantly more agreeable and cooperative (passive participant) and less submissive by their flatmates. They showed significantly less eye contact with the confederate in the social interaction paradigm and gave significantly fewer helplessness messages during the game. They spoke faster on the reading task after the social interaction. This study provides evidence that reboxetine increases cooperative social behaviour and increases social drive, which might be important for social adaptation.