The Guide to the Design of Concrete Overlays using existing methodologies is a product of the National Concrete Pavement Technology Center at Iowa State University's Institute for Transportation. The guide provides decision makers and practitioners with straightforward, simple guidance for the design off concrete overlays using existing methodologies. The guide focuses on four commonly used methods: The method described i the 1993 American Association of State Highway and Transportation Officials (AASHTO) Guide for Design of Pavement Structures, 4th edition; The method described in the AASHTO Mechanistic-Empirical Pavement Design Guide, Interim Edition: a Manual of Practice; The American Concrete Pavement Association (ACPA) modified method for bonded concrete overlays of asphalt pavements; The Colorado Department of Transportation method for bonded concrete overlays of asphalt pavements. The guide discusses specific design assumptions, deficiencies, and strengths inherent in each method, as well as step-by-step design examples for typical pavement sections. This guide is intended to be used in conjunction with the corresponding design procedures' documentation/references, such as the 1993 AASHTO Guide for Design of Pavement Structures and/or computer software for the AASHTO Mechanistic-Empirical Pavement Design Guide and ACPA methods.