We investigate individual differences in behaviour within an ultimatum game with advance production. It is a simple bargaining game, in which the size of the ‘pie’ to be distributed between two parties depends on both players' monetary investments. One player, the ‘proposer’, has to state a demand, which can be accepted as it is or rejected (with the consequence of zero return for both players) by the second player (‘responder’). We find that global personality measures contribute significantly to the explanation of both demands and rejection decisions. Proposers who score high on independence and tough-mindedness, two global personality dimensions with affinity to selfishness, demand higher return shares than proposers who score low on these dimensions. This is particularly true when the proposer's cost share is low, i.e. when a high demanded return share cannot be justified by a concern for equity. In this situation there is a strong conflict between economic rationality and equity. Regarding rejection decisions we find that reciprocity oriented responders (i.e. persons who are either emotionally unstable and extraverted or emotionally stable and introverted) reject a proposal more often than others. Rejection of an unsatisfying offer is interpreted as an act of angry retaliation (negative reciprocity) against an interaction partner who violates the social norm of equity. Copyright © 2001 John Wiley & Sons, Ltd.