JT is widely believed that international capital mobility has been increasing over recent years and that this contributes to greater interdependence among the various world economies. In particular, it is felt that greater capital mobility serves to inhibit the effectiveness of any single country's monetary or fiscal policy, depending on the degree of exchange rate flexibility.' In addition, some observers suspect that high capital mobility serves as a conduit for the transmission of economic disturbances among nations.2 In light of these issues, there are two fundamental empirical questions associated with international capital mobility. The first is whether the degree of capital mobility has in fact changed over recent years. The second is whether any noted change in capital mobility has altered the effectiveness of monetary and fiscal policy and the international transmission of economic disturbances. In this article we address the first question, for as a practical matter, if capital mobility has not changed, the second question is moot. It is our purpose to apply a technique for determining the presence and timing of significant changes in capital mobility and for detecting whether capital mobility has been increasing, decreasing, or remaining constant over time. In the process we will also compare the stability of alternative capital-flow models. Section I defines capital mobility and presents two models of international capital flows. These models, which have appeared in one form or another in the literature over the past decade, represent alternative hypotheses regarding the determinants of short-term capital movement. Section II estimates these models using a specific set of data. Section III describes the statistical method to be used to identify the timing of structural shifts in the capital flow models. It also analyzes the results of applying this method and draws inferences about changes in capital mobility over the sample period. Section IV summarizes the findings and conclusions.