Calculations have been performed of scattering and absorption self-shielding effects in the activation of bare and cadmium-covered Au, In, and 1/υ detectors in infinite slab geometry in both monodirectional (beam) and isotropic flux, for a range of detector thicknesses. Energy loss on scattering is included. It is found that the calculated activation rates agree well with published data on detector activity vs cadmium thickness and with measurements of the sandwich type. The effect of scattering is to increase the activity of the detectors over what would be observed in the absence of scattering, in a beam flux, and to decrease it in an isotropic flux. These effects are due almost entirely to scattering from the cadmium covers rather than from the detector. The contribution to the activation from neutrons scattered once in the cover is found to decrease markedly with detector thickness for the resonance detectors, and to remain more or less constant for 1/υ detectors, over a range of practical thicknesses. Effective cadmium cutoff energies have also been computed for the zero-thickness detectors and are in agreement with previously published tabulations. Tables of correction factors for scattering and for absorption self-shielding are presented.