Previous negotiation research has mainly dealt with cognitive and motivational processes and their impact on the quality of negotiation outcomes. What has been neglected so far is how the process of social interaction between the negotiating parties affects the quality of outcomes. Specifically, it remains an important question how the social interaction between negotiating parties is superior respectively inferior to other forms of confict intervention that do not involve social interaction between the conflicting parties (e.g. first-offer arbitration). Group research has continously shown that social interaction within groups does not always lead to anticipated process gains but rather to process losses. Applying these findings to the field of negotiation research one may predict that - dependending on certain preconditions - one should also expect to find process gains and losses in negotiations. The major goal of the present reserach is to investigate and define conditions leading to process losses versus gains in negotiations.