Almost all result for group decision support systems (GDSS) have been obtained in a United States context, based on conventions and culture of American group processes. This paper reports on the construction and testing of a prototype GDSS to support international negotiation. The system was shown to work and to provide gains in both the quality of the interaction and the attitude toward the decision reached. Although the prototype system is narrow in scope, focusing on two specific cultures and a single scenario and uses simple and limited technology, the results obtained suggest that computer-based intercultural GDSS can help people in staving focused, in managing the added complexity of multinational negotiation, and in interacting effectively with one another.