The American Medical Association's Guides to the Evaluation of Disease and Injury Causation (Causation) is an important component of the AMA Guides library and delineates a type of evaluation that is distinctly different from a diagnostic evaluation, a treatment planning evaluation, a prognosis evaluation, or an impairment evaluation. Causation provides a protocol for determining whether a clinical presentation, in the context of a legal or administrative claim, may be credibly attributed to a claimed cause. This article presents the evaluation protocol from Causation, provides self-assessment questions (so users can check how well they complied with the protocol), highlights the protocol's value as a model for scientifically credible practice in general, and clarifies that the protocol is relevant to claims that involve issues related to forensic causation. Courts and administrative systems have an extremely unfortunate emphasis on opinions from experts rather than on facts. The protocol from Causation is a good example of how clinicians can focus on facts and avoid surrendering to the court or administrative system's emphasis on opinions. The protocol is standardized, objective, fact-based, and scientifically credible and involves the following: establish a diagnosis; apply relevant findings; obtain and assess evidence of exposure; consider other relevant factors; scrutinize the validity of the evidence; and evaluate results and generate conclusions.