With the advent of strain controlled fatigue testing, strain gages and the local strain approach for fatigue analyses, designers must be able to assess the state of strain in a notch in order to predict the structural integrity of many mechanical components. A great deal of research effort has been expended over the past thirty years to develop fundamentally sound techniques for estimating cyclic notch strains using only elastic stress information and elastic-plastic axial material data. Neuber's rule has become the most widely utilized approach for engineering notch strain estimation. The original approach has undergone a wide variety of modifications for its use in cyclic loading and fatigue analyses. This paper reviews the origin of Neuber's rule and its development for use in fatigue design. The limitations of the approach are discussed, along with the recent efforts by several researchers to overcome these restrictions.