The authors examine the empirical determinants of debt maturity structure using a maturity structure measure that incorporates detailed information about all of a firm's liabilities. They find that larger, less risky firms with longer-term asset maturities use longer-term debt. Additionally, debt maturity varies inversely with earnings surprises and a firm's effective tax rate but there is only mixed support for an inverse relation with growth opportunities. The authors find strong support for the prediction of a nonmonotonic relation between debt maturity and bond rating; firms with high or very low bond ratings use shorter-term debt. Copyright 1996 by University of Chicago Press.