A study has been made of the relative thermoluminescence response to alpha- and beta-radiation of six phosphors (two types of natural fluorite, CaF₂:Mn, CaF₂:Tb, CaSO₄:Mn and quartz) using samples which are thin compared to the range of the alpha-particles. The alpha- and beta-radiations induce the same glow peaks, but at low doses (less than100 rads) the TL response per rad of alpha-radiation (3.7 MeV) is less than that per rad of beta-radiation in all the glow peaks studied. The alpha-efficiency ranges from 53 per cent for CaF₂:Mn to 2 per cent for quartz (110°C peak) at 3.7 MeV and decreases with decreasing alpha-particle energy. At higher doses (10⁶-10⁷ rads) the TL responses to alpha- and beta-radiation become equal with in 15 per cent; most of the glow peaks are in or near saturation at these doses. The higher the beta-dose at which a peak saturates, the higher the <alpha. -efficiency (at low doses) of that peak. The results support the interpretation that the alpha-efficiency is low because the phosphor is near or in saturation in the localized region near the alpha-path. This interpretation is given quantitative support by a theoretical calculation of the localized energy-density.