Instead of looking at the impact of specific third party actions or behaviors on negotiation outcomes, the authors studied the effects of anticipated intervention on the negotiation process. Third party power (ability to force an agreement on deadlocked negotiations or merely recommend one) and generalized reputation (favorable or unfavorable) were manipulated in a laboratory experiment to determine their effects on negotiator behavior, perceptions, attributions, and satisfactions. Questionnaires were used in measuring the latter three categories of results. Reliable differences in pre-intervention impact of third party agents possessing differential power were found. One such finding was that those anticipating a high power agent felt more pressure during bargaining and took longer to reach agreement than those in the low power condition. With regard to perceptions, significant and consistent interactions between third party power and reputation were also found. In sum, this study demonstrates the importance of constituent forces on negotiator behavior. (SJL)