The exponential integral functions of the first and second kinds, E1(b) and E2(b), and the secant (Siever’s) integral, F(θ0,b), are useful in calculating radiation fluxes. Values of these functions vary rapidly with the argument b, so that useful tabulations are voluminous and interpolation is difficult. Related functions have been defined whose values vary slowly with the argument b and which are readily amenable to linear interpolation. Thus, accurate flux calculations depend only on the availability of an adequate table of the exponential function e-b. Compact tables of these related functions and of three other functions useful in flux calculations are given in this Note, together with illustrations of their use in shielding formulas.