As global water scarcity increases, both scholars and leaders have suggested that water will be a leading cause of future armed conflict. Yet other scholars argue that states typically cooperate rather than fight to manage their shared water resources. We address these arguments by examining the management of internationally shared rivers in the Americas, Western Europe, and the Middle East from 1900–2001. We propose hypotheses on the factors that lead states to become involved in disagreements over shared rivers as well as the factors that lead them to negotiate over these disagreements. Heckman probit analysis suggests that water scarcity – found by past work to be an important influence on armed conflict over rivers – is also an important influence on peaceful efforts to settle river problems; river claims are more likely where water supply is lower and demand is greater, but negotiations are also generally more likely in these same situations. Furthermore, while the existence of river treaties does not prevent the emergence of river claims, the presence of at least one treaty over the specific subject of the claim provides an important starting point that greatly increases the likelihood of negotiations over such claims. We conclude that the more pessimistic views of water management are missing an important part of the story. States are much more likely to negotiate in the most dangerous situations, and institutionalization of river resources can make an important contribution to negotiations over any disagreements that do emerge.