The main reason why the rate of corporate bonds with the same maturity is different is default risk. The difference between safe bond (government bond) and risky bond is called default premium.Well known institutions like Moody’s, Standard & Poor’s and Fitch show us a classification scheme how much risky the bond is, depending on a number of characteristics of the underlying corporation. (9)Another feature that makes difference of rate of bonds with the same maturity is callability. When there is a callability on a bond, issuing corporation can repurchase it at a given price before maturity. So, It’s a bad option for investors and the value of bond is lower than non-callable bond.Last feature that makes difference is conversion option. A bond with conversion option can be changed to common equity at a given ratio. It’s the good option for investor, so, the value of the bond with conversion option is higher than the bond without conversion option.ReferencesElton, Edwin J., Martin J. Gruber, Stephen J. Brown and William N. Goetzmann(2003), Modern Portfolio Theory and Investment Analysis, Sixth Edition, New York: John Wiley & Sons.Ali Umut Irturk (2006), Term structure of Interest Rates, University of California, Santa Barbara, California.James C. Van Horne (1980), The Term Structure: A Test of the Segmented Markets Hypothesis, Southern Economic Journal, Vol.46, No.4 (Apr., 1980)Hyoung-Seok Lim(2005), Estimation of the Term Structure of Interest Rates and its Features:Korea’s Case, Economic Analysis Vol 11, No. 2, Korea Bank, (2005)