The chapter presents the theoretical basis of the digital image correlation method and examples of its application in relation to strength tests. This method is a particularly useful tool for the analysis of load-bearing structures operating under conditions of advanced deformations after loss of stability. In such a situation, the confrontation of the results obtained through experimental research and numerical analyses may be the basis for determining the correctness of the solution. Both the deformation fields on the surface of the tested elements can be compared, as well as selected, representative relations between displacement and load, called equilibrium paths. The results of the research allow us to conclude that correctly combined DIC and FEM results are a highly effective research tool in determining the deformation of structures in the full spectrum of the load realized. Registration of the displacement field over the entire area of the studied structure allows the identification of both the global form of deformation and local effects. Recording can take place with a specific frequency, which, in combination with the information about the load level assigned to each stage, allows for the analysis of the history of deformation of the structure. An unquestionable advantage of the DIC method is also the independence of the possibility of conducting research on the type of material from which the object is made, thanks to which research is not limited only to model tests but can also be carried out in the case of real objects. The tests themselves can be carried out in almost any operating conditions, depending on the configuration of the measuring system. A limitation in the use of digital image correlation systems is the fact that the result of the tests is the field of deformation recorded only on the surface of the tested object, which, except in the case of objects with relatively uncomplicated geometry and constant thickness, makes it impossible to directly determine the state of stress in the tested elements. In such situations, it is necessary to use the results of numerical calculations.