This study develops a model based on current corporate finance theories which explains stock returns associated with the announcement of issuer exchange offers. The major independent variables are changes in leverage multiplied by senior security claims outstanding and changes in debt tax shields. Parameter estimates are statistically significant and consistent in sign and relative magnitude with model predictions. Overall, 55 percent of the variance in stock announcement period returns is explained. The evidence is consistent with taxbased theories of optimal capital structure, a positive debt level information effect, and leverage-induced wealth transfers across security classes. THERE IS AN EXTENSIVE theoretical literature concerning optimal capital structure.' However, there is little empirical evidence of a relation between changes in capital structure and firm value. In the best known test of an optimal capital structure model, Miller-Modigliani [15] reported evidence of a positive relationship between firm value and leverage which they attributed to a debt tax shield effect. Their results are suspect, however, because of statistical problems they encountered when attempting to adjust for differences in the firms' asset structures. Since only regulated firms were examined, there is also some concern that their empirical findings were caused by the regulatory environment in which these firms operate. No strong evidence of a relation between a firm's value and the size of its debt tax shield has been uncovered since the Miller-Modigliani study.This study estimates the impact of a change in debt level on firm values. Two forms of capital structure change are examined: issuer exchange offers, and recapitalizations. The results indicate that both stock prices and firm values are positively related to changes in debt level and leverage; senior security prices are negatively related to these capital structure change variables. This evidence is consistent with models of optimal capital structure and with the hypothesis that debt level changes release information about changes in firm value. especially Robert Hamada, for their considerable help and encouragement. This is based on a chapter of my dissertation written at the University of Chicago. I have also benefited from the suggestions of the participants in the many finance workshops where this paper was presented. I also wish to thank the many U.S. corporations which voluntarily co-operated in this study. An earlier version of this paper was presented at the Western Finance Association meetings in Jackson Hole in June 1981. I take sole responsibility for any remaining errors. 'See, for example, Modigliani-Miller [16, 17], Kraus-Litzenberger [10], Scott [19], Miller [14], and DeAngelo-Masulis [5].