Results are summarized which provide the basis for development of the proposed ASTM standard test method for measuring and presenting very slow cyclic rates of fatigue crack propagation. The technique for obtaining very slow rate data as K decreases with crack extension is described. Data are reviewed that show the individual and combined effects of various precracking and testing procedures, loading rates, and other testing parameters. The data are used to demonstrate the utility of the method and its limitations. Guidelines are given for the minimization of transient growth rate processes which can confound interpretation of the data. Analytical procedures for fitting near-threshold data are also discussed.