Micro-surfacing has been widely used by several transportation agencies including the Ohio Department of Transportation (ODOT) as a preventive maintenance treatment in order to extend the service life of a pavement structure. The current ODOT specifications require placing a tack coat on an existing pavement surface prior to the application of a micro-surfacing mix in order to improve the bond strength along the interface between the two materials. Some industry professionals argue that tack coat is not necessary in micro-surfacing applications. However, the risk of not using a tack coat may include premature failure due to poor bonding between the micro-surfacing mix and the pre-existing pavement surface. Therefore, this unique research was initiated to evaluate the bond strength between micro-surfacing mixes and existing pavement surfaces with and without the application of tack coat in order to determine if tack coat is needed in micro-surfacing applications.  This presentation will provide information on the comprehensive field and laboratory testing programs that occurred and highlight the findings and recommendations.