There are two major peer-reviewed, institutional guides to forensic programme delay analysis methods. One is the Society of Construction Law’s Delay and Disruption Protocol 2nd ed. (2017) and the other is Association for the Advancement of Cost Engineering International’s (AACE) Recommended Practice on Forensic Delay Analysis: RP29R-03 (2011). The recently revised Delay and Disruption Protocol addresses the principles relevant to delay and disruption with its focus on being both a useful guide to resolving issues in a timely manner through its core principle “do not wait and see” and also a resource for guidance on the resolution of delay disputes. Its world-wide recognition and influence make it an immediate forceful presence in forensic delay analysis outside of the United States. Inside the U.S., and to a more limited degree in Canada, AACE’s RP29R-03 guidance on forensic delay analysis, and particularly its catalogue of delay methods, is often used by experts in delay litigation. The two guides each have a fundamentally different focus when it comes to delay: the former on principles to be applied in dealing with delay and the latter on recommended steps for forensic programme delay analysis. This paper provides an overview of each guide and identifies where there are material differences in the treatment of delay, and why that is so.