Abstract Phenomenological models for electron-hole pair production in scintillators are reviewed. All models provide similar results when compared on the basis of consistent definitions. The assumption of constant loss parameter K is untenable. The loss parameter K( E) was calculated from first principles by employing a dielectric response function derived from the Callaway model. The rapid variation of K( E) suggests replacement of K by an effective threshold displacement, ΔE, which is appreciable for semiconductors but negligible for insulators. The prediction of high conversion efficiency, β ≅ 1.0, implies low transfer efficiency, S < 1, in most insulators.