Abstract A theory of the tensile strength of powders, incorporating the effect of powder density, particle size distribution and interparticle force, has been developed. It enables the experimental results for different size fractions of each of five materials of different chemical and physical nature to be correlated with the particle size distribution. The large variation of tensile strength with small changes in density is interpreted to be a manifestation of the dependence of the interparticle force with surface separation of particle-pairs. A law of corresponding states is also established and it correlates the tensile strength data of the five materials. It is suggested that the functional form of the interparticle forces is very nearly the same for the five materials. An estimate is made of the energy and length parameters that characterise the interparticle forces involved. The practical use of the correlations obtained for the prediction of tensile strength from particle size distribution determination alone is discussed.