Current methods of field testing components in agricultural and industrial equipment are described in this paper. This presentation concentrates on experimental methods in which instrumented components are studied with experimental load and stress analysis techniques. It does not cover standard product engineering durability-type testing in which components are run under actual operating conditions for an extended number of hours to assess their durability. The first part of the paper outlines field test techniques, instrumentation, and mobile test laboratories. More specifically, methods of using brittle coatings to locate highly stressed areas will be outlined along with field strain gaging techniques. The use of oscillographs and tape recorders located in an instrument van, which follows the product under test, will be shown. Differentiation will be made between tests used to directly estimate component fatigue life and tests which are used to accumulate load data to confirm theoretical design analysis or to set up durability tests in the laboratory. Because these test procedures are intimately associated with the subsequent use of the test data, the second part of this paper will describe the methods of analyzing the data to make life decisions and will include a description of laboratory materials properties tests and component tests which provide the necessary fatigue life data against which the field test data are compared. The final part of this paper will cover some of the new methods being studied to automate the reduction of field test data through the use of computers.