Is the yield on a bond assuming the bond is redeemed by the bond issuer at the first call date. Yield to call differs from yield to maturity in that yield to call uses a bond's call date as the final maturity date (most often, the first call date). 

Conservative investors calculate both a bond's yield to call and yield to maturity, selecting the lower of the two as a measure of potential return. Like yield to maturity, yield to call calculates a potential return: it assumes that interest income on a particular bond is reinvested at its yield to call rate; that the bond is held to the call date; and that the bond is called.