Effective energy cutoffs have been calculated on an IBM7090 computer for Cd, Gd, Sm, and B filters as functions of filter geometry, the ratio of Maxwellian to epithermal flux (assumed to be 1/E), the lower energy limit of the 1/E flux, the energy corresponding to the Maxwellian most probable (modal) velocity and filter thickness. The geometrical configurations were spherical (which on the assumptions madc is equivalent to a beam flux case), cylindrical and slab. By the use of two or three different filters (Cd and Gd and perhaps Sm) it should be possible to detect resonances in the thermal to cutoff energy regions, in addition to measuring resonance integrals and thermial cross sections of unknown nuclides. (auth)