Available experimental evidence concerning absorption in x-ray targets, corrected for fluorescence due to the continuum, is generalized to give the formula, f_p=(1+agammachi)^-2, in which f_p is the primary x-ray absorption factor, gamma=(E_o^1.65- E_q^1.65), E_o(kV) is the operating voltage, E_q(kV) the critical excitation voltage, chi=mu cosec psi, mu is the mass absorption coefficient for the respective target and line, psi is the x-ray emergence angle, and a=1.2x10^-6 g/cm². The presumed effect of the atomic number of the target on f_p is overestimated by Philibert's formula. It is smaller than the statistical spread of experimental data, and can therefore be neglected.