The author discusses several consequences of the finite depth of penetration of x-radiation on the reliability of tensometric interpretation of the results of measurements of lattice strains. Attention was given mainly to materials based on α-Fe. In applying conventional tensometric methods, the finite depth of penetration of radiation has a detrimental effect on stress with the gradient in the direction of the surface normal mainly in cases in which the calculations are based on the lattice strains which correspond to small angles.