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This paper looks back over our work of the last fifteen years on two methods for the analysis of
fatigue and fracture at stress concentration features: the Crack Modelling Method (CMM) and the Theory of
Critical Distances (TCD). We describe the general principles and philosophy of this work, which was envisaged
primarily as a solution to an engineering problem, using finite element analysis to estimate the behavior of
bodies of arbitrary geometry and loading. The general principles of the two methods are described along with
some discussion of their relative merits and applicability. The CMM is essentially a one-parameter method
(equivalent K value) and so has some limitations which the TCD does not, since it uses at least two parameters
(length L and equivalent stress) or three if multiaxial conditions are considered. We have extended the TCD
into its most general form, including finite life fatigue under mutiaxial and variable amplitude conditions, and
can now confidently advocate its use in industrial design.