The use of computer-based simulation models has a long history in areas suc
h as environmental planning and policy-making, and particularly in water ma
nagement. Policy making in these areas is often characterized by inherent c
onflict among diverse stakeholders with divergent interests. Although simul
ation models have been shown to be helpful for such problems, they are typi
cally under the control of a technical analyst or governmental agency and a
re not available to negotiators in real time. Recent trends in computer tec
hnology and user expectations raise the possibility of real-time, user-cont
rolled models for supporting negotiation. But is such accessibility likely
to be helpful? This study used a "compressed" longitudinal experiment to in
vestigate the impacts of different scenarios of accessibility of computer-b
ased simulation models. The task was based on a real-life problem in Colora
do River water management. Results revealed no significant differences amon
g conditions for either solution quality or satisfaction. These results sug
gest that the common notion of "more is better" may be inappropriate, and r
esources for improving computer support of negotiation might best be focuse
d elsewhere.