The Matrix Force Method is frequently used in the stress analysis of complicated aircraft structures. It assumes as unknown quantities, or redundancies, groups of internal loads, and yields stresses and displacements in terms of a set of unit loads. Lately, this method has been extended to include effects of uneven temperature distribution. With large structures, the method is most effective with high speed digital techniques which allow considerable computational detail to be stored in the computer memory. Theoretically, the method is based on the Castigliano theorem of least work, equivalent formulations being possible. Hence the method is applicable to elastic problems of the first order only, i.e. strains infinitesimal, structural distortions not affecting equilibrium conditions markedly.