A revenue bond is a special type of municipal bond distinguished by its guarantee of repayment solely from revenues generated by a specified revenue-generating entity associated with the purpose of the bonds, rather than from a tax. Unlike general obligation bonds, only the revenues specified in the legal contract between the bond holder and bond issuer are required to be used for repayment of the principal and interest of the bonds; other revenues (notably tax revenues) and the general credit of the issuing agency are not so encumbered. Because the pledge of security is not as great as that of general obligation bonds, revenue bonds may carry a slightly higher interest rate than G.O. bonds; however, they are usually considered the second-most secure type of municipal bonds.