This manuscript provides a user's guide for the human reliability analysis (HRA) method known as "A Technique for Human Event Analysis" (ATHEANA), which the U.S. Nuclear Regulatory Commission (NRC) documented in NUREG-1624, Rev. 1, dated May 2000. As the first publication of its kind, this user's guide describes both the quantitative and qualitative ATHEANA analysis approaches, fully describing the revised quantification approach and presenting a simpler description of the other ATHEANA elements needed to perform an HRA as part of a probabilistic risk assessment (PRA). Toward that end, this user's guide strives to present the steps for applying ATHEANA in a straightforward and succinct manner, so that HRA experts can easily and effectively apply the technique. Consequently, although the authors relied on NUREG-1624 as a primary resource for its development, the NRC is publishing this user's guide as a standalone document, such that it can be used by analysts to apply the ATHEANA technique without the need to use NUREG-1624.