In recent years, the volume of municipal bond financing has increased dramatically. This, in conjunction with soaring interest costs and a perhaps strengthened awareness of risk by investors, has created a need for municipalities to curtail borrowing costs. One means by which municipalities have attempted to accomplish this goal is through the purchase of municipal bond insurance. Three firms offer private municipal bond guarantees at substantial premiums. It is their claim that municipalities can gain interest cost savings in excess of the fee paid for coverage.Municipal bond insurance assures timely and full payment of interest and principal to investors in the event of default by the issuer. Demand for this type of insurance has grown significantly since 1975. The actual amount by which borrowing costs are reduced, however, is largely unknown, since very little empirical evidence has been examined to determine the actual interest cost savings of municipal bond insurance. To date, only three empirical studies [3, 4, 71 have attempted to quantify the interest cost savings of private municipal bond insurance. Of these studies, none is comprehensive, nor are any firm conclusions derived. Each study attempts to accomplish a different goal, consequently there is very little collaborating evidence among them. As a result, the value of municipal bond insurance is unclear.This study uses a regression model to empirically investigate the effect of insurance on the true interest cost (TIC) to the issuer. The T I C of the issue serves as the dependent variable with independent variables reflecting characteristics of the issue, the issuer, and the market. The effect of municipal bond insurance on the cost to the issuer is captured by a dummy variable. This paper is presented in four sections. Private municipal bond insurance is discussed in Section I. Section I1 contains a presentation of the model, and the empirical results are presented in Section 111. O u r conclusions are summarized in Section IV.