Thermoluminescence (TL) and photoluminescence studies have been carried out on CaSO 4 :Tb, CaSO 4 :Ce and CaSO 4 :Tb,Ce phosphors with the aim of studying energy transfer process in the CaSO 4 :Tb,Ce phosphor. CaSO 4 :Tb,Ce shows TL peaks at 150, 220, 320 and 400 o C. Changes in Tb and Ce concentrations influence the relative heights of these glow peaks. Co-doping with 0.1mol% of Ce in CaSO 4 :Tb enhances the sensitivity of 320 o C TL peak by a factor of 15. Fluorescence results show that there is energy transfer from Ce to Tb ion. The defect centres formed in CaSO 4 :Tb,Ce phosphor are studied using electron spin resonance technique. The 320 o C glow peak correlates with a centre (SO 3 - radical) with g-values: g | | =2.0061 and g =2.0026.